Penny Hofstadter (née "Unknown") is the series' first and always main female protagonist. She lives in Apartment 4A with her husband Leonard Hofstadter across the hall from Sheldon Cooper, and Amy Farrah Fowler who live in apartment 4B where Penny used to live. Her full first name is possibly "Penelope" as implied by "The Barbarian Sublimation", and her maiden name has never been revealed. But due to her recent marriage to Leonard, her last name is Hofstadter. She unknowingly married her ex-boyfriend Zack Johnson. That marriage was annulled in "The Thanksgiving Decoupling".
An aspiring, but mostly unsuccessful actress, she was born on a farm near Omaha, Nebraska, and worked at The Cheesecake Factory as a waitress until she quit in "The Occupation Recalibration" (S7E13) to take up acting full time. Penny was the original female lead in the show before being joined by Bernadette Rostenkowski and Amy Farrah Fowler and in season 8 started working at the same company as Bernadette.
She has always been Leonard's love interest since the pilot, with the two dating briefly in the first episode of the second season, for most of the third season, and they rekindled their romance in "The Recombination Hypothesis". As of "The Gorilla Dissolution", she and Leonard became engaged and were married at the start of season 9 in "The Matrimonial Momentum".
Even though she is considered part of the guys' group, she represents the "dumb blond" for viewer context in the series with a lot of street smarts and communication skills to compensate for her lack of academic knowledge. As the series progresses, her knowledge of geeky subjects even surprises her.
Early Life (Before the show)
Penny was born in Nebraska, a small a town outside of Omaha to Wyatt and Susan. She also has one sister whose name is unknown and one brother Randall. During her childhood, Penny had issues with her father who wanted a boy and he treated Penny like one (until her brother came along), like making her play catch, calling her 'Slugger' etc. When Penny was 12, she rebuilt a tractor engine all by herself ("The Big Bran Hypothesis"), started dating at the age of 14 ("The Robotic Manipulation") and in high school, nearly became pregnant ("The Staircase Implementation") and had an active sex life that she defines as being popular.
Penny moves into Apartment 4B across from Apartment 4A where Leonard and Sheldon live. Penny had broken up with her boyfriend Kurt because he cheated on her. She asked the guys for a favor to go get her TV from his apartment, but he steals their pants and Penny apologizes for everything and later the three go out to dinner with Howard and Raj ("Pilot").
After a post-date disagreement, Penny remains friends with all four guys, becomes an integral part of the Social Group and very good friends with Leonard.
In the episode finale "The Monopolar Expedition", Penny wishes Leonard wasn't going to the North Pole
When the guys return from the North Pole, Penny has missed Leonard enough that she expresses her feelings for him and they date for most to the season.
Penny introduces her friend Bernadette to Howard as part of a Girlfriend Pact made between Howard and Leonard. Things don't go to too smoothly until the two of them rind out they both have overbearing mothers.
Penny resumes being part of the guys group and has her own friends, Bernadette and Amy. Also she realizes that she still has feelings for Leonard, especially since Leonard is dating Priya.
Half way through the season (on the 100th episode), Leonard asks Penny out and they reunite, though Penny has misgivings.
Penny works through her doubts and has a stronger relationship with Leonard, as she is now able to say "I love you" to him. They discuss marriage.
Penny finds out she is legally married to Zack after Leonard, Sheldon and Amy tell her that weddings in Las Vegas wedding chapels are real when the two thought they were fake. At the end, she and Zack fill out annulment papers and the marriage is legally annulled ("The Thanksgiving Decoupling"). Penny quits The Cheesecake Factory to concentrate on acting ("The Occupation Recalibration") and becomes engaged to Leonard in the penultimate episode of the season ("The Gorilla Dissolution").
Between the finale of Season 7 and the premiere of Season 8, Penny drastically changes her look by swapping her usual long blonde locks for a short blonde pixie-crop, a look she sports throughout the entire season. She gets a new job at Bernadette's company as a pharmaceutical rep, making excellent progress in her field as well as spending the year as Leonard's fiancée. At the end of the season, she suggests they head to Vegas to get married.
Leonard's little make out session at sea, makes their marriage have a rocky start, but they quickly reconcile though they don't move out of Sheldon's apartment (because of Sheldon going through a bad breakup, and due to Sheldon's abandonment issues). At the end of the season, when it's revealed that everyone is upset about not being part of the wedding due to their elopement, Penny suggests having a redo wedding ceremony.
Penny and Leonard have their re-wedding ceremony in a park which is officiated by Bernadette (The Conjugal Conjecture).
Penny and Leonard finally have their own apartment, Apartment 4A. In "The Cohabitation Experimentation", Amy's apartment suffered water damage, was uninhabitable and she needed a place to stay. Sheldon and Amy started a five week experiment to see if they could manage living together and moved into Penny's old apartment, Apartment 4B. It turned into a permanent arrangement in "The Veracity Elasticity". Penny also redecorates her and Leonard's bedroom.
Origin and Development
Originally, two different female leads were written for the Pilot episode. The unaired pilot episode had an alternate version of the female lead named Katie. Katie was bitter and received by audiences to be too mean to Sheldon and Leonard. Kaley Cuoco did not portray this alternate version of the female lead, but instead was hired to do the second version filmed after the unaired pilot, which was sociable and nice and was the one that the producers decided was the more interesting and appealing out of the two.
Some of Penny's comedic role in the series is rooted in her ability to execute practical and simple solutions to problems of which the guys try to solve through complicated or scientific means. For example, in the episode "The Pants Alternative", Sheldon reveals that in spite of his ability to talk excessively to people in small groups, he has a severe case of stage fright, and wouldn't be able to accept an award. While Leonard tries to get to the root of his problem through a psych evaluation, and Raj attempts to use meditation, Penny solves the problem by having him buy a new suit and getting him intoxicated right before he makes his speech.
As the series developed, Penny's character took on the theme of being the virtual polar opposite of Sheldon, which created a unique relationship between the two characters. Penny's relationship with the other guys is usually perceived as something of an older sister, or a mother in some cases with Sheldon. She has also had a romantic, on-and-off relationship with Leonard.
When she first met the guys in the Pilot, Penny was writing a screenplay about a girl from Lincoln, Nebraska who travels to Los Angeles at the age of 18 to become an actress, but ends up working at The Cheesecake Factory instead. When Leonard asks if the screenplay was autobiographical, she replies that it isn't, because she is from a small town outside of Omaha, Nebraska.
Penny moved into the apartment building because she split with Kurt, her boyfriend for 4 years. She says she still loved him, and insinuates he cheated on her. The shower in her apartment was broken at the time, so the boys offered her theirs. Her apartment is sloppy and disorganized, but Penny appears to like it that way.
She is either oblivious to or completely aware of her effect on the boys, because within minutes of meeting him, she asked Leonard to retrieve her television set from Kurt's apartment, which he immediately set out to do. Penny is aware of Leonard's crush on her, and it is hinted throughout the series that some of the feelings are reciprocated. At the end of season one, Penny goes on a date with Leonard. Leonard is nervous, and Penny slightly withdrawn, but they nonetheless share a kiss.
In season two, there was some initial enthusiasm between Penny and Leonard. However, they later develop insecurities concerning their relationship. Penny was worried that she was not smart enough for Leonard, and lied about graduating from community college because she thought it would make Leonard respect her. The relationship quickly deteriorated and she goes back to dating different guys. Leonard showed Penny some literature on Pasadena City College and she interpreted it as him wanting a woman with more education and they break up.
She gives relationship advice to Sheldon and Leonard fairly often: Leonard, when he has problems with Priya or Stephanie, and Sheldon when he's with Amy. She also starts to become geekier through the guys. She makes inadvertent references to Star Trek, and, thanks to Sheldon, becomes addicted to Age of Conan. She also dates Stuart, who runs the comic book store. However, when Penny and Stuart are making out, she accidentally calls him Leonard, and as a result, they stop seeing each other.
When she learns that the guys are going on an Arctic expedition, she is visibly upset, buys Leonard a farewell gift, and tells herself, after speaking with him, that she wishes he wasn't going.
In season three, when the boys get back from the expedition, Penny kisses Leonard the second she sees him; however, Leonard and Penny's relationship has a rocky start because they have some trouble getting used to being more than friends, but they eventually start a relatively stable relationship.
Green = Appeared,
M = Mentioned, V = Voiced, C = Cameo,
Dark Grey = Did not appear,
Penny is somewhat naive and not thoroughly educated, but has a lot of common sense and street smarts. Her dream is to become a famous actress, a goal she never seems to waver from until season 8. She is very kind-hearted and empathetic toward people though she can blow up when made mad, which prompted Leonard to refer to her as "The Incredible Hulk" after she went off on Howard. She believes most guys are nice and has been hurt a lot. When someone shocks her, she tends to bat her eyes at them while she is considering her response. She also walks away when frustrated with people like Sheldon or situations she can't believe or understand. She knows how to throw out wise-cracks and is very loyal to her man as long as she is not betrayed. She also has a tendency to deny doing things that are embarrassing or she suddenly realizes are embarrassing. In the first season she seemed very naive, but has appeared smarter in later seasons and more complicated in situations with her female friends. She also has a habit of being selfish and throwing her friends under the bus. For example, she sold Sheldon out to the court officials for running a red light, despite the fact he had done it to help her after she had dislocated her shoulder, simply because she didn't want the ticket.
Her maiden name has never been revealed. As of 2015 she took the last name of her husband, Leonard Hofstadter.
Penny And Randall's Sister is mentioned as having shot her husband while they were both intoxicated.
It is known that she has a nephew who turned 13 in season two, likely the son of Penny and Randall's sister.
When Christy (Penny's friend from Omaha) comes into town, Penny reveals that she has a brother and at least one male cousin, as she claims that Christy slept with the former while being engaged to the latter.
Her brother, Randall, also works in a meth lab, though it's not clear if it is the same brother Christy slept with. This fact is first hinted at in "The Pirate Solution" as Penny describes him as 'kind of a chemist' and tells Leonard that he would like him. It is finally confirmed in "The Rhinitis Revelation" when she asks God to make her brother stop cooking meth, but without involving the authorities. In season 7 in "The Hesitation Ramification", Penny mentions that her Dad gathered all the relatives together to see her scene on NCIS, which included getting her brother a day out of rehab. They also bought a large sandwich to share. When her scene is cut, Penny mentions that the sandwich and her brother are gone and as far as she knows her brother is on the way to Mexico. She also mentioned wanting to postpone her wedding with Leonard until he gets paroled.
Sheldon implies Penny's mother, Susan, is overweight and in "The Flaming Spittoon Acquisition" says that her mother must have used cannabis when she was expectant with her. In "The Status Quo Combustion", Penny is discussing her engagement with her mother, tells her that she is NOT pregnant and that that is unusual in their family.
In season two, "The Maternal Capacitance", as Penny is explaining to Beverly that her father stopped playing catch with her when she developed breasts, she quotes her mother talking to her father, and suggests his name is Bob, though it is later revealed in "The Boyfriend Complexity" to be Wyatt. Her father visits Penny and begs Leonard to get back with her because he wants grandchildren who don't live in a house on wheels.
In "The Conjugal Conjecture"; Penny is happy to have her family visiting. She has a close relationship with her father and a little more tense one with her mother. She takes her brother with a smile and a joke.
- Father: Wyatt
- Mother: Susan
- Brother: Randall
- Sister: Unnamed
- Brother-in-law: Unnamed
- Nephew: Unnamed
- Cousin: Unnamed
- Pet Pig: Moondance (now deceased)
- Husband: Leonard Hofstadter
- Father-in-law: Alfred Hofstadter
- Mother-in-law: Beverly Hofstadter
- Brother-in-law: Michael Hofstadter
- Sister-in-law: Unnamed
- Brother-in-law: Unnamed
- Presumed Sister-in-law: Unnamed
Penny considers herself a waitress/actress though she has told Leonard that she is a "professional" actress despite her short acting resume. Her income is derived from working at the Pasadena Cheesecake Factory as a waitress and living off the guys in Apartment 4A. In "The Occupation Recalibration" (S7E13) she quits the job as a waitress and declares she would engage herself in the acting area full-time. Leonard never discourages Penny when she joins them for takeout meals, piggybacks on their Wi-Fi connection and paying for her movie tickets and other bills in spite of Sheldon's protests to get to her to stop. In a podcast interview with Wil Wheaton, director Kevin Smith told her that he thought she was talented, and would love for her to audition for "Clerks 3". Ultimately, Penny did try out, but felt that her audition stunk. Currently, Penny is a pharmaceutical representative/salesperson, at Bernadette's company Zangen and is taking a break from acting. According to her boss Dan she is his third best salesperson though she admits to Leonard she doesn't like flirting with doctors just to make sales. At the beginning of season 10, she gets assigned a better sales territory.
As of Fall 2015, her acting career credits consists of:
- A topless role in a low budget horror film "Serial Ape-ist". This movie happened before she moved into Apartment 4B (in the Pilot), but is not revealed to the audience until "The Hofstadter Insufficiency" (S7E01).
- A one night showcase production of the musical Rent ("The Loobenfeld Decay", S1E10).
- A production of The Diary of Anne Frank, performed over a bowling alley; ("The Terminator Decoupling", S2E17; later mentioned in "The Psychic Vortex", S3E12 and "The Recombination Hypothesis", S5E13).
- A hemorrhoid commercial ("The Skank Reflex Analysis", S5E01; later mentioned in "The Recombination Hypothesis", S5E13; in "The Transporter Malfunction", S5E20. She says she gets a residual check from her commercial, which presumably still refers to this one).
- Acting class production of A Streetcar Named Desire ("The Monster Isolation", S6E17).
- A big part in NCIS that was cut from the final show ("The Hesitation Ramification", S7E12).
- Playing an ape/human clone in Serial Ape-ist 2, Monkey See, Monkey Kill ("The Indecision Amalgamation", S7E19) Fired in "The Gorilla Dissolution" after she wanted to improve her performance.
- In "The Fetal Kick Catalyst", Penny attends Van Nuys Comic-Con to sign autographs for her work in "Serial Ape-ist 2: Monkey See, Monkey Kill" and is surprised how popular the movie is, but is reminded how terrible an actress she is. She had her big break and her five minutes of fame for one movie.
PlatonicThe Panty Piñata Polarization" when Penny messes up Sheldon's laundry night. Despite their differences, Sheldon and Penny are very close, and are quick to help each other. They have taken care of each other on multiple occasions; often times doing things they really don't want to do to make each other feel better. Penny has stated that they are friends.
Major examples are when Penny takes care of Sheldon when he is sick, and when she lets him stay at her apartment when he gets locked out, even letting him sleep in her own bed. Sheldon was also quick to come to Penny's aid when she called for help after falling in the shower and dislocating her shoulder, going so far as to drive her to the hospital, despite not knowing how to drive.
Many of these occurrences end with Penny singing Soft Kitty to Sheldon to make him feel better or when he is sick; Sheldon sang it to her on one occasion as well. One of the biggest examples of their friendship is that despite his own rule of avoiding physical contact with people, Penny was the first person Sheldon hugged on the show.
Penny remains one of only four people he's hugged who aren't members of his family, the only others being Leonard, Wil Wheaton and Amy Farrah Fowler. To date, Sheldon and Penny have hugged two times: once in "The Bath Item Gift Hypothesis" and again in "The Large Hadron Collision". Sheldon also is in the habit of insulting Penny when he asks her for a favor.
In "The Werewolf Transformation", Penny convinces him to let her cut his hair since his barber is in a coma. She listed times she's taken care of him, saying that she's taken him to Disneyland, kicked a bully in the nuts for him, sings him Soft Kitty when he's sick, and that he's even seen her naked once. Sheldon eventually agrees to let Penny cut his hair.
In "The Closure Alternative", Penny decides that she is passionate about her friends and tells Sheldon that she is glad he is in her life.
In "The Bon Voyage Reaction", Leonard asked Penny to keep an eye on Sheldon while he's gone. They hung out together and Penny took him shopping, developing a brother/sister relationship. In "The Hofstadter Insufficiency", they didn't even get on each other's nerves, and Penny played the games that Sheldon wanted to play or usually played with Leonard. Sheldon even tried to comfort a lonely Penny and let her hug him with very little objections. After Sheldon had a nightmare, he knocked on Penny's door early in the morning. He woke Penny up and all she did was ask what he wanted, she was neither mad nor disgusted by his intrusion, indicating a good, stable, friendly relationship.
In "The Cooper Extraction", Amy points out to the gang that most of them would not know each other if Sheldon had not been part of their lives. Penny feels that Leonard would never have successfully asked her out at the Cheesecake Factory, while Leonard suggests that she would have ended up with Zack. In the Zack story, he spent all the rent money on some magic beans. Amy thinks that if Amy and Leonard were out of the picture, the lusty Penny would try and seduce her neighbor Sheldon much to Penny's disgust and the guys' amusement.
In "The Anything Can Happen Thursday Recurrence", Penny takes Sheldon to a psychic at a time when he can't decide what new problem of science to follow after string theory is disproved. The psychic knows that he has trouble with his girl and that following that relationship will give him the answers he seeks.
In "The Intimacy Acceleration", Penny and Sheldon conduct a psychological experiment which should result in the couple instantly falling in love. Sheldon wants to do it because he thinks its poppycock, and Penny does it because she gets to ask Sheldon a lot of personal questions that he has to answer honestly. They admit a lot of truth about themselves like Penny wishes she were as smart as the others and that she uses comedy to cover up insecurities. Finally they stare into each other's eyes for four minutes and decide that they do have a new found intimacy though just as a brother and sister.
In "The Matrimonial Momentum", Leonard and Penny go to Las Vegas and decide on their wedding package, which includes a live stream that allows their friends to watch from home. Sheldon keeps pushing Amy to decide whether she broke up with him and she does in the middle of the ceremony after he offensively insults her to her face. Amy and Bernadette run out of the room, while Raj takes Sheldon home, leaving only Howard and Stuart to catch the "I now pronounce you Husband and Wife" bit.
In "The Separation Oscillation", Leonard has a nightmare that Penny got even with him by making out with Sheldon. This spurs Leonard to try to make things right. Later Sheldon gives them a wedding present - a trip to San Francisco for the three of them.
In "The 2003 Approximation", Leonard finally moves out to live with his wife Penny; however, in the end Penny agrees that they will spend at least half their night back in Leonard's old room.
In "The Celebration Experimentation", Sheldon ran into the bathroom after overwhelmed by the birthday party they were throwing him. Penny went into talk to him claiming that it was okay if he wanted to be there. She would probably have tortured him along with his sister and friends at his birthday party, but now that she knows him, he is one of her favorite people. Penny would be happy to spend his party in the bathroom with him. Sheldon doesn't want people think that that is weird. Penny explains that everyone things he is weird, but still loves him and came to his party anyway. Later at the party, Penny makes him hug her and he has upgraded his feeling toward hugs to mildly irritatingThe Killer Robot Instability". Leonard makes Penny go and apologize; however, she ends up breaking Howard's nose when he tries to kiss her. Their dynamic remains the same for the most part throughout the series, but begins to change when Howard begins to date Penny's friend Bernadette. Although Penny is not a fan of him, she admitted that she considered Howard a friend in "The Engagement Reaction", although they rarely hang out outside of the group. Howard flirts with Penny much less and becomes more casual towards her after he begins his relationship with Bernadette, which Penny obviously enjoys, although she still pokes fun at him.
Like with all other women except his mother and sister (and thus one would assume all female relatives), Raj is unable to speak to Penny unless he is intoxicated or on medication. They hang out within the group a lot and Penny occasionally attempts to tease him into talking to her. After she goes to a People magazine reception with him, he introduces her to his parents as his girlfriend, despite their preference of him finding an Indian lady. Raj begins to like Penny as the series goes on and the two end up getting inebriated and appear to have had intercourse. Once he can speak to her sober, they become each other's confidants.
Later, Raj tells Penny that nothing physical happened between them as she instantly asked if he had had protection. He had trouble putting it on, and she tried to help, but he ejaculated prematurely. Raj asks Penny not to tell anyone and Penny promises to keep silent. Raj attempts to actually date her, but she tells him she just wants to be friends. Despite their rough past, Penny attempts to find a girlfriend for Raj and comforts him when he needs it. She also invites him along to their ladies' night out while the guys play their Dungeons and Dragons Christmas game. He discovered he had come over his selective mutism when he was able to talk to Penny about his breakup with Lucy without being under the influence in "The Bon Voyage Reaction".
They also hang out with the guys together once Howard starts dating Bernadette. In "The Countdown Reflection", because Bernadette wants to get married to Howard before he goes into space, Penny, along with Amy, Sheldon, Leonard and Raj become ordained as ministers to so they can officiate at the wedding ceremony.
Penny is notably upset when she is in the middle of Bernadette and Amy's fight during "The Parking Spot Escalation". She is really hurt once Amy takes a swing at Bernadette with her purse hitting Penny in the face and breaking her nose.
Bernadette gets Penny and interview at Zangen as a pharmaceutical sales representative in "The Locomotion Interruption". Though she does poorly in the job interview, Penny and her interviewer bond over their mutual fear of Bernadette. Penny calls her scary and something of a bully. She gets the job because neither of them wants to confront her. Later on, Penny shows a great deal of maturity in wanting to do a good job especially after Bernadette pestered her to study up on the company's products. Bernadette thinks Penny got the job because her interviewer really loves her. Bernadette gives Penny some advance material to studying before she begins her training and pushes her to study it and they get on each other's nerves. Amy is in the middle and finds them both confiding in her making her feel very popular. Finally Penny and Bernadette settle down and she helps Penny learn her company's product line.
Penny makes Bernadette face up to her bullying ways in "The Champagne Reflection". Her boss Dan is still afraid of her and she yelled at him and his grandson after they lost the three-legged race at the company picnic. His grandson called her the mean kid with the big boobies. Bernadette is horrified when she realizes how everyone perceives her. Her father had taught her to not take any crap, and she can be even cruel with some of her comments without even knowing it. She thought she was the sweetest person she knew and should be in a tree baking cookies like a Keebler elf. She goes to apologize to Dan and finds out that due to his fear of her, they were paying for her daily coffee even after the company stopped doing that and gave her a private toilet on her floor that was meant for everyone. She now feels like she has to leave the company and starts crying. Dan wants her to stop and promises to keep paying for her coffee and then ups it to getting her an espresso machine. Bernadette has found a new way to get what she wants.
Bernadette once admitted that Penny getting a shorter haircut was a "brave" choice when everyone else said they hated it.
The two gradually form a tight friendship and continue to spend more time together and are quick to aid one another whenever the other needs it. Amy is aware that Penny is the planet that her social life revolves around and quickly reverses her course if she is mad at her or is annoying her. Amy gave Penny a large unflattering painting of the two of them to celebrate their friendship, which at one point the former realizes the latter hates. Penny rushes over to Amy's apartment to rescue their friendship and re-hangs the painting in her apartment on the fourth wall (facing the audience).
In "The Shiny Trinket Maneuver", when Amy had her argument with Sheldon, Penny took Sheldon to the jewelry store to buy a gift. Sheldon ends up getting Amy a tiara. Penny is more than happy putting the tiara on Amy, which makes Amy ecstatic. In "The Weekend Vortex", Amy confides in Penny when she had an awful time at her aunt's birthday party because Sheldon backed out on his promise to attend an MMORPG marathon. Penny gets them to play quarters where the loser will need to drink beer. Amy turns out to be very good at the game from all the time she spent as a child throwing coins wishing for friends, and as a result, Penny gets intoxicated. She convinces Amy to make a scene and the two barge into the guys' apartment as they are in the middle of their marathon. Amy fails to keep up her ruse of leaving Sheldon for a make-believe character named Arman, and Penny comes to her rescue by telling Sheldon the truth. Penny is also very upset to be in the middle of the argument between Amy and Bernadette over
Howard's parking space in "The Parking Spot Escalation", especially after Amy accidentally hit her in the face with her change-filled purse, giving Penny two black eyes and a broken nose.
In "The Cooper/Kripke Inversion" Penny asks Sheldon if he is ever going to sleep with Amy. After Sheldon says that it is a possibility, Penny gets very excited for her friend. In "The Love Spell Potential", Penny tells Sheldon's and Amy's "D&D" characters to "do it" in the game, which upsets Amy and causes her to leave. In "The Spoiler Alert Segmentation" Penny ruins Amy's chance to move in with Sheldon because she is ready for Leonard to move in with Penny. Sheldon also didn't want Amy moving in either. To prove that she could do it, Amy tells everybody that she should move in with Penny which Penny also disapproves of. In "The Anything Can Happen Thursday Recurrence", Amy did admit to Leonard that she is jealous of the close personal friendship between Sheldon and Penny and how comfortable he is around her.
In "The Hook-up Reverberation ", Penny wonders how she could get Raj's new girlfriend Emily to like her. Amy says that she could hang around her pretending to be her friend and before you know it you're in her apartment drinking her wine and eating her food. Penny says that that won't work even though Amy's suggestion mirrors her own relationship with Penny.
In "The Space Probe Disintegration", Penny and Amy finally get the chance to choose what they'll do with Leonard and Sheldon (as they usually call the shots in that regard). During their outing, it's revealed that Penny hypocritically does the same thing when hanging out with Amy. However, Amy insists that she's fine with it because she promised herself that if she got friends, she'd do anything they said. Penny tells her that a lot has changed since then, especially considering that not only does she have great friends, she's also smart, pretty, and has a boyfriend now. At that moment, Amy is given the opportunity to make everyone do what she wants.
Penny was shown to have a good relationship with Leslie Winkle, Leonard's lab partner at the university.
Priya was envious of Penny because of Leonard's previous relationship with her, and eventually asked him to stop communicating with Penny. Though Penny did so, she became angry towards Priya for dating Leonard, as she had only recently realized she still had feelings for him. The friendship is restored when Priya becomes friendly with Penny in the engagement reaction episode where they strike up a friendly conversation and bond in the process, although Penny remains silently jealous. When Priya's relationship with Leonard ended after admitting that she slept with her former boyfriend a few weeks ago, Penny and Leonard start dating again.
Penny wanders into Leonard's apartment begging to have a cup of coffee, and it is here that she first encounters Stephanie. Dr. Stephanie Barnett asks Leonard who this woman is who comes into his apartment in the morning in her underwear. Both Penny and Sheldon make it difficult for Leonard to explain. He describes Penny as one of many neighbors who wander throughout the apartment building which has no dress code. Leonard exclaims that he has never slept with Penny. Sheldon adds that it wasn't from a lack of trying. Sheldon also describes Stephanie as a valuable roommate which Leonard denies that they are living together. Penny goes to check out Leonard's bedroom and finds enough of Stephanie's stuff that Leonard realizes that they are living together.
In "The Hook-up Reverberation", Penny and Leonard meet Emily for the first time,and she treats Penny rather coldly. At Bernadette's suggestion, Penny stops by Emily's office to do her sales pitch in front of a real doctor. Penny does her pitch enthusiastically; however, Emily ignores her. She doesn't like that Penny had crawled into bed with Raj. Though Penny is mad at Raj, he gets them together and they apologize to each other. After they part, both women say how much they hate the other one.The Maternal Congruence", and previous to "The Convergence-Convergence" and appears to be very fond of her. He toasts the happy couple at their wedding re-do and is interrupted by his ex-wife. Penny notes what happens when Alfred and Mary Cooper leave early for the hotel. She also loves the fact that Leonard and Sheldon's parents have gotten together.
In "The Dependence Transcendence", Bert hosts a Caltech party that only Amy and Penny attend. He feels that Amy is the coolest girl at work and that Sheldon is cool only because he is dating Amy. As the girls are leaving, he tells them that he is in love with both of them.
Kurt is Penny's ex-boyfriend at the beginning of the series. In the pilot episode, Leonard and Sheldon went to his apartment and tried to retrieve Penny's TV set from him, but they did not succeed and returned home without pants. Penny left him because he cheated on her, but he was still invited to her Halloween party in "The Middle-Earth Paradigm". When Penny experienced financial difficulties, Leonard and the guys tried to convince Kurt to pay Penny back money he owed her; at first Kurt refused, but eventually he paid Penny back to date her again.
A guy she met and was together with for six months. They never really talked and Penny never learned what the TJ stood for. TJ is only mentioned once in The Recombination Hypothesis during Leonard's imaginary date with Penny and it is unclear if TJ is an actual character from Penny's past or an imaginary character from Leonard's dream.
Doug is a guy with whom Penny just had a long-weekend fling just to get over her relationship with ex-boyfriend Kurt.
Mike is a guy who Penny dated in "The Nerdvana Annihilation". In "The Tangerine Factor", Penny broke up with Mike after he posted several "details about their sex life" in his blog. She attempted to reconcile with him after Leonard unintentionally convinced her to do so, only to walk in on him having sex with another woman. After these events, Leonard took his chance and asked Penny out on a date.
High school boyfriend that she had a pregnancy scare with. They were seen in her bedroom joyous over the negative pregnancy test results.The Hamburger Postulate", when she hears of his failed attempt at a relationship with Leslie Winkle, though the sign is seen only by the audience. Despite these signs she continues to date other men, though she regularly visits Leonard's apartment every day to see him.
She and Leonard went on their first date in the finale of the first season, but they were unable to start a relationship because Penny feared he would get bored with her due to his high intelligence compared to her own. Regardless, Leonard continues his pursuit of Penny throughout the second season, even going as far as confronting her towering ex-boyfriend, Kurt in an effort to retrieve the money he owes her.
After Leonard returns from his three-month research trip at the North Pole, Penny immediately kisses him, having missed him greatly. Leonard happily returns her affections and they later make love for the first time.
Despite another rocky start, Penny remains happy with Leonard throughout most of season 3, forming the kind of stable relationship that she hadn't seen in over two years.
Things went downhill, however, when Leonard told Penny "I love you," and became angry and insecure at her unwillingness to reciprocate. The pressure he places on Penny--along with a heated argument that occurred between the two during a bowling match--eventually caused her to abruptly end their relationship, leaving Leonard heartbroken. Wil Wheaton pushes her so that she leaves making her bowling team forfeit.
They later agree to stay friends, even though it's clear that Penny has never stopped liking Leonard, and as she revealed in a game of truth or dare with Amy and Bernadette, only broke up with him because she became scared after Leonard told her he loved her. When the girls point out that she could lose Leonard to another woman as a result of her decision, Penny storms into her bedroom and slams the door.
Though Penny keeps an emotional distance between herself and Leonard throughout the fourth season, her feelings for him are hinted at on more than one occasion. Once was during a New Year's Eve party at the comic book store, when Penny stares uncomfortably at Leonard while she kisses her date, Zack Johnson. Earlier that evening, Penny let it slip out to Leonard that he was one of the reasons why she had been feeling sad recently.
Their friendship eventually becomes strained when Leonard begins dating Raj's sister Priya, causing confusion for Penny as she starts to reconsider her feelings for him. The situation gets worse when Penny and Priya grow jealous of each other, forcing Leonard to cut his ties with Penny permanently. During their time apart, Penny becomes very close with Amy and Bernadette, who provide comforting support and help her understand the depth of her emotions regarding Leonard's new relationship.
In the season finale, Penny admits to Raj that she "screwed up," and that she never should have broken up with Leonard. Coincidentally, Leonard told Raj how he ached for Penny the same way a year earlier.
Penny again reveals her regret in season 5 to Sheldon (without mentioning Leonard directly), telling him that he should never take his relationship for granted. The result was Sheldon thinking that she had a thing for him.
Penny finally makes her move after Leonard and Priya break up later in the season, asking Leonard out to the movies, but hiding her feelings by keeping things casual and telling him that sex was off the table. Leonard misses the hint however, and the night turns into a disaster when the two attempt to make each other jealous by flirting with other people they encounter during the date. They do make up in the end, and Leonard's hopeless infatuation for Penny surfaces when he becomes submissive once more in an attempt to sleep with her.At the spur of the moment in "The Recombination Hypothesis", Leonard asks Penny out on a date after he imagined what getting back with her might be like. He also realizes he over analyzes everything too much. Their real date ends successfully and they agree to take their relationship slow in "The Beta Test Initiation".
In "The Launch Acceleration", Penny suggested that they move up their relationship. However, Leonard ruins the mood when he asks her to marry him during intimacy. They later meet and Penny, unlike their first split, managed to reject his proposal and still stay in a relationship with him. During "The Countdown Reflection," they watch Howard's space launch while holding hands to comfort each other.
Things remain awkward between them in the months following the failed marriage proposal. Raj, who was butting into one of their dates, insisted that Penny tell Leonard that she loves him, but she was not ready and threw him out of the apartment.
Penny later expresses more doubts about whether she truly loves Leonard to her friends in "The Decoupling Fluctuation," describing her passion for him as "boring" compared to her previous relationships. She nearly breaks up with him at the conclusion of the episode, but changes her mind at the last moment and ends up sleeping with him to hide the truth, especially after he looks at her with a "sad puppy dog eyes" face. The next day, Leonard again expresses his unparalleled love for Penny via text message, making her feel even guiltier as she struggles with whether or not she wants to be with him.
Their relationship takes a completely different turn however, when Penny visits Leonard's workplace with Amy and sees Sheldon's attractive assistant Alex flirting with him in the cafeteria ("The Higgs Boson Observation"), causing Penny to become jealous and confused about her feelings for Leonard once again.
Her feelings continue to grow in "The Holographic Excitation," when Penny decides to drop by Leonard's laboratory after Amy and Bernadette urge her to take a more active interest in his work. Despite her lack of knowledge in science, Penny becomes fascinated as Leonard uses holographic imaging to explain the basis of string theory and the holographic principle, speaking in a way that sparks her passion and earns him the kind of affection (bordering on love) that he had last seen during their first night together after he returned from the North Pole.
In "The 43 Peculiarity", Penny is working with a British fellow student named Cole on an oral class project. Leonard is jealous so he follows him down the apartment stairs and tells him to watch out for "Penny's boyfriend" since he is a gang member. Penny is upset with Leonard and the two later meet in the hallway and have an argument. Penny tells him that she cannot believe that he does not trust her and that he embarrassed her in front of Cole who knew who he was since his picture is on her refrigerator. Penny continues to tell him that he is the one she is with and unwittingly mentions that he knows that she loves him. Leonard is stunned and tells her that that is the first time she ever said that she loves him. He then interprets her stunned reaction and asks if they aren't going to make a big deal about her confession. She agrees and runs off to cry.
In "The Egg Salad Equivalency", after Alex asks Leonard out to dinner and he didn't tell Penny about it, she begins to feel really insecure about their relationship. Penny also gets angry with Leonard when she discovers that he enjoyed the attention from Alex. Leonard apologizes by playing her an apologetic song on his cello and reassuring her that nothing will ever happen between him and Alex. She decides instead of feeling bad, she will do something about it. First, she looks into science classes at college, but they sound boring. Then she buys some geek glasses to look smart, which does affect Leonard as he pulls her into his bedroom.
In "The Bakersfield Expedition", she develops an interest in comic books and Thor's hammer.
In "The Spoiler Alert Segmentation", Leonard suggests that he move in with Penny after he again gets exasperated with Sheldon. He asks her if she's all right with it, but she only agrees not to hurt his feelings and even tells Sheldon. When Amy confronts Penny since she can't move in with Sheldon, Leonard over hears. Penny tells him that he never asked her if she was ready and Leonard ends up back in apartment 4A.
In "The Tangible Affection Proof", Leonard takes Penny out to dinner for Valentine's Day. Penny feels that all the effort never meets the expectations. Penny sees a former boyfriend proposing to the girl that broke them up. Leonard again tries to propose and Penny stops him. That night Leonard tells Penny that she made a mess of the whole evening. Penny finally admits that she has commitment issues and the obvious path of their relationship ending in marriage scares her. Leonard then puts the responsibility of proposing on her and she should do it when she's ready. In the end, she does ask him to be her Valentine, to which he accepts.In "The Closure Alternative", Penny was concerned about the passion Leonard showed for science, comics and various television shows while she had no passion in her life. Her dreams had always been to become a famous movie star and live a glamorous life. Anything less than that she felt was settling. Her epiphany comes that she is passionate about her boyfriend Leonard and all her wonderful friends.
In "The Bon Voyage Reaction", Leonard takes a job working on a Stephen Hawking expedition in the North Sea for four months over the summer. Penny will miss him, but knows that it is a good opportunity and sends him off. At the airport, she is fussing over him like his wife sending him off on a business trip. She also has to watch Sheldon over the summer, too.
In "The Hofstadter Insufficiency", Leonard hurts Penny because he seems to be having such a great time on the ship; she thinks that he is not even missing her. In "The Deception Verification", Leonard makes up for it by showing up early and hides in her apartment so that they can spend time together a couple before telling the gang that he's back. It works until Amy and Sheldon find them together after they think that Penny is cheating on Leonard.
In "The Raiders Minimization", Penny purchases a psychology book that Beverly Hofstadter has written about all his problems growing up called The Disappointing Child. Leonard is extremely embarrassed, so Penny does whatever he wants to make him feel better, including having sex in his lab. He mentions her actions to Howard, who failed to repeat the results on Bernadette, so Bernadette tells Penny. She dresses up for sex to tempt him, and then for revenge makes him Skype with his mother to discuss him using his mother's past with him to manipulate elements of his sex life.
In "The Romance Resonance", Howard makes a romantic gesture to Bernadette by writing her a song. Leonard mentions that Penny never does anything like that, except for sex which doesn't count. Penny is determined to romance Leonard. Raj can only suggest that she cook for him or reenact a scene from a romantic movie. Finally after a candlelight dinner, Penny puts on some romantic music, spreads rose petals into her neatly cleaned bedroom and presents Leonard with a first edition of his favorite book from when he was growing up, The Hitchhiker's Guide to the Galaxy. Unfortunately, Leonard had already purchased it after he had seen it in a secondhand bookstore with her. Penny gets upset telling him about all the thoughtful things he had done for her and shows him her collection. An airplane ticket to Nebraska so she could see her family, a rose given to her "just because", and the eleven-page letter he wrote her after the first time they slept together. Leonard was very touched that she kept all these things. He then kisses her, showing that Penny did do something romantic; it's also revealed that she kept the very first pregnancy test she used when they started having sex.In "The Thanksgiving Decoupling", Penny reminisces about a Thanksgiving she had in Las Vegas with former boyfriend Zack Johnson which included one of those silly fake weddings. Penny appears devastated when her friends inform her that the wedding was real and she is married. Penny and Leonard argue about how quickly she should get her annulment so Penny invites Zack over to their Thanksgiving dinner at Howard's mother. Zack appears as dimwitted as ever telling them that breaking up can be hard on the kids which they don't have. Finally, Penny and Leonard make up and she tells him that the next time she gets married it will be for real, for love and (jokingly) or for money.
In "The Hesitation Ramification" (S7E12), Penny is frustrated that she has nothing to show for herself after ten years in LA. Leonard points out that she does have him. A tipsy Penny then gets down on one knee and proposes. Leonard hesitates to answer her and she storms out. Leonard is worried that Penny is now going to break up with him. In the next episode "The Occupation Recalibration" (S7E13), Penny tells Leonard that he did the right thing since she was a mess that night and they stay together.
In "The Table Polarization", the gang wants to add a dining room table to Apartment 4A which Sheldon objects to. Penny gets Leonard to pick out a dining set that she likes and gets Leonard to stand up more against Sheldon. Sheldon objects to Penny changing Leonard to stand up against him. Penny points out that Amy has changed Sheldon who agrees and then decides to break up with Amy.
In "The Mommy Observation", Penny seems to feel that if she were a successful actress and had to move around, Leonard would leave his job even if it was a tenured position to follow her since she would be making more money.
In "The Proton Transmogrification" Penny asks Leonard to marry her to get their marriage proposal rejection score from 2 to 1 to even. She also gets upset when she keeps getting all the Star Wars in-jokes during their Star Wars' Day celebration.In "The Gorilla Dissolution", Leonard and Penny get back in her apartment after getting fired from her movie. Penny wants to start making smarter decisions about her life. She says that they could get married and Leonard asks her to be serious. Leonard asks her if he is a smart decision, like choosing a healthy boring bran muffin. Penny doesn't care what pastry he is because she is CHOOSING HIM. Leonard is still talking about being a pastry like a strawberry Pop Tart that she is excited about. Penny tells him to forget about it. Leonard does want to marry her, but feels that she is just feeling sorry for herself because she was fired. Penny explains that it may seem that way, but getting fired made her think that fame and fortune is not what is going make her happy. Leonard wants to know what she needs. "You, you stupid strawberry Pop Tart!" Leonard finally says that he guesses that he is in, which also bothers Penny. Leonard then retorts that it is an excited "I guess I'm in" and they agree that they are engaged which seems somewhat anti-climactic. To change the mood, Leonard pulls a ring out of his wallet that he has had for a couple of years, gets down on one knee and asks Penny formally. Penny says "yes" and he slips the ring on her finger that still has ape hair glued to it and they embrace.
In "The Status Quo Combustion", Leonard and Penny announce their engagement; however, the gang is more excited about Raj and Emily hooking up. Leonard goes searching for the missing Sheldon and finds him at the railroad station leaving time to think about all the changes in his life. Leonard wants him to come home, but Penny convinces him that he should let him go.
In "The First Pitch Insufficiency", they go on a double-date with Shamy where Sheldon is bragging about their relationship is so much better than theirs. Shamy has an 8.2 out of ten for relationship stability based upon well proven criteria. Leonard looks at it; however, Penny doesn't want to take the test. She already has his doubt and doesn't need them confirmed. They are engaged and still have very little in common which scares her. It also scares Leonard, but he still want to face all their problems together. His reassure really touches Penny and Amy who would like Sheldon to say things like that.
In "The Prom Equivalency", Amy and Bernadette throw a do-over prom on the roof of the apartment building. Penny is at first reluctant to attend the party because they always disappoint her, but Leonard tells her that he really wants to take the most beautiful girl to the prom, this time. She wears her old red prom dress. The roof is decorated wonderfully and Penny really gets into the mood. While others are still getting there, Penny and Leonard dance along without any music on the roof. First they conclude that they probably would not have approached each other if they had been at the same prom. They are both definitely in a romantic mood, while Penny is also glad they aren't having the drama normally seen at proms.In "The Space Probe Disintegration", Leonard tells Sheldon that his attitude is why he and Penny are not living together. After a tearful period thinking about them him moving out, Sheldon let's him go one night a week to stay at Penny's. Sheldon still sleeps on her couch that night.
In "The Commitment Determination", Sheldon keeps pushing them for a wedding date. The couple insists that they aren't in a hurry, are in a good place emotionally, and are concentrating on their careers. Thinking about the wedding details, they decide on a small church wedding dressed in black tie tuxes and no releasing of butterflies. Suddenly, Penny smiles and sits close to Leonard. She tells him that she's free that night. They could go to Vegas and just get married. Leonard agrees. Sheldon is happy for them, but still doesn't want them to sit in his spot. Driving to Vegas, Penny is very happy and glad that they took their time to get to know each other so that there would be no surprises and no regrets. Leonard has one regret about a time when he was drunk and made out with a woman on his North Sea expedition. Penny is not happy, but still wants to marry him. Last seen they were still heading to Vegas. Penny is feeling betrayed. According to the production staff, Penny and Leonard will become man and wife on the premier ninth season episode.
In "The Matrimonial Momentum", Leonard and Penny are at a wedding chapel, and decide on their wedding package, which includes a live stream that allows their friends to watch from home. In the chapel, the minister asks Leonard and Penny if they had prepared vows. To Penny's surprise, Leonard has. He says that they are made from atoms that have traveled over 14 billion years to create them so they can come together as a couple and make each other whole, which overwhelms Penny. Penny sweetly says that he is the love of her life and her best friend and improvises, quoting the lyrics to 'You've Got a Friend In Me' from the Disney film "Toy Story". The minister asks if that was from "Toy Story." Penny says it was and informs the minister that she quoted the lyrics because he loves them. Leonard gets misty-eyed and confirms that he does. Leonard and Penny are pronounced man and wife. Unfortunately, Stuart and Howard are the only ones remaining who catch it, due to Sheldon insulting Amy, causing her to finally break up with him, causing most of the group to leave. Leonard decides to carry Penny across the threshold into the suite, but huffs and puffs as he carries his wife into the hotel room. They kiss, but Penny still can't stop thinking about Mandy the girl on the boat. Leonard again insists that the kissing wasn't that great, especially since he also chipped her tooth. Penny wants to know if he feels guilty. Leonard jokingly says that he does not feel guilty because the girl had dental insurance. Leonard then adds that he does feel guilty when he sees her every day at work, freezing when he quickly realizes his mistake. Penny is now truly shocked that he never told her this fact. Instead of spending the night in Vegas, they return back to their apartments, still fighting. Penny spends the night alone while Leonard spends it with Sheldon.
In "The Separation Oscillation", Leonard has a nightmare that Penny got even with him by making out with Sheldon. This spurs Leonard to try to make things right. He finally confronts Mandy, his kissing buddy from the North Sea, about the incident and it doesn't seem to mean much to her. Leonard also realizes that he really was trying to sabotage the relationship. He went and talked with Penny and tells her. She too realizes the she has been trying to sabotage their relationship. Leonard then confesses, "I've loved you from the moment we met and I will keep loving you until the end of time." Penny is very touched and tells him that that was the most beautiful thing anyone has ever said to her. He follows with getting down on one knee and asks, "Penny Hofstadter, will you please stay married to me?" and she replies "Oh, damn it. You topped it.". She and Leonard kiss and eventually reconcile. They then head into the bedroom to formalize their marriage. Later Sheldon gives them a wedding present - a trip to San Francisco for the three of them.
In "The 2003 Approximation", Leonard finally moves out of his apartment and eventually moves in with Penny into her apartment. The sleeping arrangements are still a little complicated. Even though they are living together in 4B, they sometimes sleep in 4A, in Leonard's old room. This is due to Penny having a change of heart at the last minute after feeling sorry for Sheldon who was having a hard time dealing with his breakup with Amy and Leonard moving out. In "The Helium Insufficiency" it is also apparent that Leonard is still maintaining an office in 4A.
In "The Valentino Submergence", Leonard and Penny go out to dinner for Valentine's Say and have to wait for an hour and suffer through an unsympathetic maitre D'. Penny decides to flirt with him, gets nowhere and is called "ma'am". She tries to get him to acknowledge that they are almost the same age; however, he is 21 and she is 31. Next she drags Leonard out of the restaurant "while she is still young". After a fast food meal in the car, they look for something young and fun to do. The "Moulin Rouge" movie is too late, no skinny dipping or dancing either. They end up dressed as cupids breaking in on Sheldon's "Fun with Flags" programs yelling "Happy Valentine's Day" and that they are "young and fun".
In "The Positive Negative Reaction", they discuss having children. Although Penny says she is not in a rush, she's actually open-minded to the idea, and that someday they can.
In "The Solder Excursion Diversion", Penny stops by when Leonard and Howard are working late on their guidance system prototype and she stays helping them make parts for it. She is very happy getting to play scientist. She and Bernadette are both furious when Raj tells them that they went to go see a movie and lied to them, but all is forgiven when they return with flowers, an apology, and the offer to pay for dinner.
In "The Big Bear Precipitation", while spending the weekend in a cabin, Penny learns that Leonard has been keeping a secret bank account for emergencies because he doesn't feel that Penny can handle money due to her large credit card debt. Penny, who makes more than him, admits that she does not like her job having to flirt to get her sales; however, she will keep at it because it is the responsible thing to do.
In "The Viewing Party Combustion", Leonard get tired of the quarterly Roommate Agreement meetings where nothing important is ever discussed. Penny who has signed the latest on as an occupant of the apartment and wants to attend since she gets to lead them in the pledge. Leonard sulks about attending the meeting which makes Penny mad driving her and Sheldon over to her apartment breaking the group into two separate camps. Leonard also points out the weird brother/sister relationship she and Sheldon has which Amy is also jealous of. Penny often takes Sheldon's side due to her sibling feelings for him.
In "The Line Substitution Solution", Penny attempts to bond with Leonard's mother, Beverly, only to discover that she, like everyone else, feels insulted about their spur-of-the-moment elopement. So, to make up for it, Penny suggests another ceremony so everyone can be involved. Later that night in "The Convergence-Convergence", she tells Leonard about the idea, he agrees, and it's official.
In "The Conjugal Conjecture"; the actual ceremony is officiated by Bernadette. Penny tells him how much she loves him and how glad they did elope. Leonard just tells her how much he loves her and that he can't believe she is with him. Also that he doesn't care if he knows why.
In "The Cohabitation Experimentation", Sheldon and Amy move into Penny's apartment for a five week cohabitation experiment after Amy's apartment suffers a plumbing problem. The Hofstadter's are so excited about finally having a place of their own that they put on music (which Sheldon would never let them do) and have a private dance party in their underwear.
In "The Fetal Kick Catalyst", Penny is signing autographs for fans of the Serial Ape-ist movies where the fans think that she is a terrible actress and can't believe that the nerd Leonard is her husband. The fans sit around Leonard as he tells his story how he won the hot actress.
In "The Veracity Elasticity", Leonard learns from Howard that Penny has secretly been moving his collectibles into storage. Although he's mad that she doesn't feel guilty about it, he does understand that she really hasn't been feeling comfortable like she belongs there. He allows her to redecorate their room any way she wants it. Upon seeing Penny's new design for the bedroom, he immediately hides some of her stuff in her old closet.
In "The Birthday Synchronicity", Bernadette has a false alarm trip to the hospital before she has her baby interrupting both Lenny and Shamy who are trying to have sex.
In "The Holiday Summation", the Hofstadters cheerily head off to cut their first live Christmas tree and have a horrible experience. Leonard lets go of the ax sending it flying, the tree slips of the car roof while driving it home, Leonard collapses under the tree while carrying it up The Stairs and after getting it into the apartment, they find an animal lurking in the tree. It ends up being shoved down The Elevator shaft.The Lunar Excitation" (S03E23), he goes on a date with Penny who, allegedly due to having dated Leonard, finds his stupidity insufferable and winds up having a drunken sexual encounter with Leonard on the same night.
Penny gets back together with Zack again in "The Justice League Recombination" (S04E11), later admitting to Leonard that she only did so in order not to be alone on New Year's Eve. In this episode Zack attempts to befriend Leonard, Sheldon, Raj and Howard. He dresses up as Superman for Stuart's New Year's party, helping them complete their Justice League theme and win the contest for best group costume. He and Penny apparently broke up again sometime afterwards.
In "The Thanksgiving Decoupling" (S07E09), Penny mentions the fake wedding ceremony she and Zack went through on a Thanksgiving trip to Las Vegas three years ago. Leonard explains that those wedding chapels are real and that Penny is legally married to Zack, who also thought the ceremonies were fake. Penny realizes that she is married and is Mrs. Zack Johnson. While dinner is being prepared, Penny has annulment papers downloaded, fills them out and calls Zack over to sign them. Dense as ever, Zack wonders if he should do it to their kids. Penny reminds him that they have no children and he asks if she's sure about that, since she didn't even know she was really married to him. He signs it and they all sit down to a Thanksgiving dinner.
In "The Cooper Extraction" (S07E11), Leonard makes up a story about what if Penny would have ended up with Zack. Leonard imagines that Zack would use the money for rent to buy magic beans, and then Zack and Penny would both pee their pants.
In Zack's recent appearance "The Fermentation Bifurcation" (S09E22), he admitted that he's always liked Leonard and Penny together, especially after seeing that they got married. Zack also expresses his interest in science, and becomes slightly wiser than the others when he points out how the military could get their hands on the project that Leonard, Sheldon, and Howard are working on, as well as quickly deducing Raj's infidelity.
"Hi (Hi, Hi) (Hi, Hi)...Hi?" [Meeting Sheldon and Leonard for the first time]
"Amy's right...I do want to fling my poo at her." [To herself after seeing Priya]
"Sheldon, you forgot something...this plasma grenade. (explosion) Look, it's raining you!¨ [Teasing Sheldon after beating him in Halo]
"Okay, sweetie...I know you think you're explaining yourself, but you're really not." [To Sheldon when she can't understand Sheldon]
"Who's Radiohead?" [Challenging Sheldon at his knowledge]
"Not since I found out that the teddy bear you gave me had a webcam in it." [To Howard when he tricks her at the door]
"When I go, I usually just get hammered and ride the cable cars." [Talking about San Francisco]
"Come on, Sheldon, you can't leave. Don't you need to stay here so the mother-ship can find you when it returns?" [To Sheldon when he tries to relocate.]
"Okay, Leonard, I know I said I could handle your roommate, but I was wrong, we're going to have to break up." [To Leonard when Sheldon wakes them up at night]
"Just move your scooter before I pick it up and throw it in the dumpster!" [To Howard after he makes a dirty joke to her]
"Soft Kitty, warm Kitty. Little ball of fur. Happy kitty, sleepy kitty. Purr, Purr, Purr." [To Sheldon whenever he's sick]
"She agreed to go out with for free, what more do you want?" [To Howard about Bernadette]
"Sheldon tried to take the ring and I punched him." [After giving Sheldon a whopper in the nose]
"Bark once if you want me to call PETA." [to Cinnamon]
"They're gonna get beat up at Walgreen's." [About Howard and Raj going Goth]
"Do or do not, there is no try." [Quoting Yoda after intercourse]
"It's just rum. It stopped being eggnog about a half hour ago" [To Leonard at Christmas]
"Actually, that's not true, Leonard. Recently I've been thinking that given the parameters of your experiment, the transport of electrons through the aperture of the Nano fabric metal rings is qualitatively no different from the experiment already conducted in the Netherlands...observed phase shift in the diffusing electrons inside the metal ring already conclusively demonstrated the electron analog of the Aharonov-Bohm quantitative interference effect...That's it, that's all I know. Oh, wait! Fig Newton's were named after a small town in Massachusetts not the scientist!" [Penny unknowingly insulting Leonard's work]
"Yeah, you can't sit there... oh no, you see in the winter it's close enough to the radiator so that he's warm, but not so close that he sweats. In the summer, it's directly in the path of a cross breeze created by open windows there and there. it faces the television at an angle where it isn't direct so he can still talk to everybody, but not so wide that the picture looks distorted." [Explaining to Bernadette why she can't sit in Sheldon's spot]
"What's up, buttercup?
What's the word, hummingbird?
What's the gist, Physicist?" [Greeting Sheldon at the door]
"Leonard, look. Sheldon's hugging me!" [To Leonard as she and Sheldon embrace]
"Hey, guys, what'cha doing? Going out to discover electricity?" [To the guys with their kites]
"Who do we love?!" [As Sheldon knocks on her door]
"I got my geek on, boys!" [To the guys]
"Out of coffee, need coffee." [Coming over for coffee]
"I smell Chinese food." [Using smell to find food]
"What up, Moon Pie?" [Teasing Sheldon over the phone]
"Leonard...will you be my Valentine?" [After she agrees that she will propose to Leonard]
"Your mom still here? - Come on in." [To Leonard when asking for alcohol]
"Mrs. Cooper, hey, it's Penny. Yeah, I think I broke your son." [To Mrs. Cooper after she gets Sheldon]
"Oh, this isn't alcohol. This is a magic potion that makes me like you." [To Sheldon about playing D&D]
"I drink my potion." [To everyone as they prepare to battle imaginary ogres]
"I'm happy Leonard's found someone... not that anyone asked". [To the guys about Leonard dating Priya]
"Awww, he's got the same look my little nephew gets when he can't figure out how I got his nose." [Teasing Sheldon about why he can't figure out the magic trick]
"Sweetie, I understand you have scars that non-professional can heal." [to Sheldon]
"Well then, good news! Today's the day a girl's finally going to touch you in your little special place." [Before kicking the hacker in the groin]
"Yeah, My mom gave me the same lecture about my virginity." [To Leonard about opening the toys she bought]
"All right, Howard Wolowitz, listen up! You sign anything she puts in front of you. Because you are the luckiest man alive if you let her go there is NO way you can find anyone else. Speaking on behalf of all women, it's not going to happen - we had a meeting." [To Howard about the pre-nup]
"Oh, a couple of virgin Cuba Libres who turned out to be a little slutty... Hey you do your experiments, I do mine." [To Leonard about tricking Sheldon into getting drunk]
"Yeah, well, your Ken can kiss my Barbie." [To Sheldon about Laundry Night]
"Sheldon, that's not what girlfriends are for. Although you don't use them for what they're for, so what do I know?" [To Sheldon about relationships]
"So that means, you're a doctor, you're a doctor, you're a doctor, you're a doctor and ... Howard you know a lot of doctors." [Teasing Howard about not having a doctorate]
"No, no, no, no, I didn't forget. Um, there's this cat in a box and until you open it, it's either dead or alive or both. Although, back in Nebraska, our cat got stuck in my brother's camp trunk, and we did not need to open it to know there was all kinds of dead cat in there." (To Sheldon about Schrödinger's Cat)
"Happy Valentine's Day." [To Sheldon about getting sick]
"Apparently, the one fella tried to adjust the thermostat, then the other fella went bat-crap crazy." [Sarcastically describing Leonard and Sheldon's fight]
"You wanna turn yourself into some sort of robot?... Okay, here's my question: Didn't you already do that?" [To Sheldon about living longer]
"Holy crap on a cracker!" [Shuddering over Sheldon and Ramona]
"Aw, honey, the buses don't go where you live, do they?" [To Sheldon about touching his onion rings]
"And what kind of doctor removes shoes from asses?" [Sarcastically threatening Sheldon about being in her apartment]
"What up, Shel-bot?" [To Sheldon's computer monitor]
"What's up, buttercup?"
"What's the word, hummingbird?"
"What's the jist, physicist?
- Penny was 21 years old at the beginning of the show, which means she is the youngest of the gang. Penny is a Sagittarius, meaning she was born between November 22 and December 21. In "The Prestidigitation Approximation", Howard does a fake magic card trick in which the sum of the digits of one's birth date, excluding the year, are used to get the number of the card to be selected. Penny turns over the fifth card, making her birthday in the span of the Sagittarius one of four possibilities: November 30th, December 2nd, December 11th, or December 20th. If Penny's birthday is November 30th (1+1+3+0=5), it would match the birthday of Kaley Cuoco (Saturday, November 30, 1985) exactly. The only possible birth date of Penny would be Monday, December 2, 1985 if one alternatively interprets the rules of Howard's card trick as requiring one to turn over the card corresponding to the sum of the digits of the month and adding the day. In The Platonic Permutation Leonard confirms that Penny's birthday is December 2. Though David Underhill refers to Penny as a "gorgeous 22-year-old" in "The Bath Item Gift Hypothesis" (air-date December 15, 2008), he could have simply estimated her age, as it certainly appears to be close to Christmas and the episodic events probably span days rather than weeks (if one were to ignore the hypothesis that the air date is reality in the show). In real life, the 29-year-old Cuoco is the youngest of the group, and approximately 13 years younger than Jim Parsons, who is the oldest of the group.
- Penny has been seen naked by three of the boys, Leonard, Sheldon and Raj, so far in the series. Howard is the only person who hasn't seen her naked and he better not since he is married to Bernie.
- Leonard had relations with her multiple times in season 3, 5, 6, 7, 8 and 9. (Only one time in season 5.)
- Sheldon peeked at her while trying to help her get dressed due to her injured shoulder in "The Adhesive Duck Deficiency".
- Raj and her got undressed and had a one night stand in "The Roommate Transmogrification" (though it was revealed in the episode after that they never had intercourse at all).
- In "The Robotic Manipulation", Sheldon calculates that Penny dated an estimate of 193 (±8) men and had relations with approximately 31 of them.
- Penny grew up on a farm and rebuilt an entire tractor engine all by herself at the age of twelve.
- Penny was a junior rodeo champion.
- The previous occupant of Penny's apartment was a 200-pound transvestite named Louie/Louise with a skin condition, who worked as a police officer, according to Sheldon. He is seen during a flashback in "The Staircase Implementation", where he refers to Sheldon as 'crazy'.
- Penny is the only member of the main set of characters whose last name has not been spoken or revealed, but Bill Prady has said it eventually will be. It will probably be revealed at some point after her and Leonard's marriage.
- In "Pilot," Penny claims to be a vegetarian, but will eat fish and the occasional steak.
- Penny often smells like either vanilla (because she wears the oil) or cheesecake (because she works at The Cheesecake Factory). Sheldon has also stated in "The Decoupling Fluctuation" that she uses green, apple-scented shampoo, insisting that she switch back to that from coconut.
- Penny's acquaintance Christy could be a reference to Kaley Cuoco's time on Charmed. Penny was also the name of the witches' grandmother. The reference may also apply to Penny's father's name, Wyatt.
- Her beliefs in psychics, ghosts, astrology, voodoo, and other 'superstitions' (but not healing crystals) may be also be a reference to Kaley Cuoco's time on Charmed.
- Penny eats Chinese food with a fork and double-dips her egg rolls (unappealing attributes, according to Sheldon).
- In "The Staircase Implementation", it is revealed that Penny was almost a teenage mother.
- Penny is often kindhearted and shows empathy toward others, but can become quite fierce when provoked. She has yelled at Sheldon, Raj, and Howard when they annoy her too much, and Leonard when she's angry at him.
- When under pain medication, Penny exhibits some of Sheldon's behaviors.
- Penny has an amazing sense of smell.
- Penny believes in psychics, ghosts, astrology, voodoo, and other 'superstitions', but not healing crystals.
- Penny went to community college, but dropped out for unspecified reasons. She goes back near the beginning of the sixth season, taking one history course. By the middle of the season, she is also taking an acting class, and at the beginning of season 7, she is taking a psychology class as well.
- Every member of the gang (except Stuart and Emily) have seen Penny with black eye(s).
- A running gag of the show involves Sheldon knocking on Penny's door and saying her name after every three knocks. He repeats this statement thrice or until she answers the door.
- Penny often resorts to freeloading. When Sheldon's mom pointed out her disapproval of a top (shirt) belonging to Penny, she said that she had received free drinks by wearing that top. It is also known that, while she was dating Leonard, she never paid for her movie tickets. She also gets free meals from hanging with the guys since her portions were always paid by Leonard; she said they were loans, but she knew Leonard would not ask her to pay it back. She also gets free internet by using Sheldon and Leonard's wi-fi -- leading Sheldon to regularly change the password to ones which accuse her of freeloading.
- She turned down Sheldon's offer for a date (although Sheldon only asked her to make Amy jealous) as Penny was the only other woman that Sheldon knew well.
- Penny was a bully in high school, making fun of a girl with a stutter and taping another girl up and leaving her out in a corn field until the next morning; she (along with the entire Zangen staff) would later become subjected to Bernadette's bullying ways. Being friends with Bernadette and Amy was her redemption for her mean girl ways. Even marrying Leonard was also part of her redemption. She even apologized to the girl she bullied in high school. It's never confirmed if the girl (now woman) accepted it on the phone.
- Penny is remarkably adept at games in general, excelling at Halo, Age of Conan, and chess, checkmating Leonard on her first try (though the latter may have been because, as Sheldon has pointed out, Leonard is terrible at chess).
- Penny owns a red 1980's Volkswagen Cabriolet Mk1 convertible car. Featured in several episodes, the car appears to be in a bad condition, which is not helped by Penny, who pays no heed to the warning lights of the car. While sitting in her car, Sheldon will continuously remind her that the 'check engine' warning light is on, an action that irritates Penny tremendously. Penny is a very bad driver: in "The Guitarist Amplification", a point of argument between Penny and Leonard is when Penny finds out that Leonard complains about her driving behind her back. Later in the episode, she runs a stop sign without even noticing it, and then, when Leonard mentions it, she looks back to find it, and Leonard, panicking, shouts "EYES ON THE ROAD, EYES ON THE ROAD!" She had gotten a car from Leonard in "The Friendship Turbulence" when her car broke down and she could not afford to fix it.
- When Penny is shocked, she bats her eyelashes several times while considering a reaction.
- Over the course of the series, Penny has exhibited traits of alcoholism. She is often seen drinking wine or other harder beverages while in her apartment, both alone and in the presence of her friends. She often seems to use wine as a means to deal with her issues. She will many times use this method on her friends as well to help them deal with their problems, most notably when she realized alcoholic drinks are able to help Raj overcome his selective mutism, or to help Sheldon overcome his stage fright.
- She often says "OMG" or "Oh My God" when shocked, to the annoyance of Sheldon.
- Despite Amy's admiration for Penny, she does realize her limitations in her intelligence and her acting career.
- In "The Scavenger Vortex", no one wanted Penny on their team because she was a "liability".
- Penny thinks that the wedding chapels in Las Vegas perform fake weddings.
- Penny was unknowingly married to Zack Johnson and took his last name until the annulment.
- In "The Adhesive Duck Deficiency", when Sheldon was dressing her, due to her dislocated shoulder, he had to put her hurt arm into the sleeve. He grabbed what he thought was her arm, but was actually her breast.
- It was discovered by Sheldon that Penny has a Chinese character tattooed on her right butt cheek.
- Though Wyatt (Penny's father) has been featured in the show, "The Maternal Capacitance" references the name of Penny's father to be called "Bob".
- So far Penny has been the only person in The Social Group to witness a Shamy kiss onscreen.
- In the count of the number of proposals to each other, Penny has three, Leonard has three through the time they got engaged.
- She is called "Blondie" by Leslie Winkle.
- It is rumored that Lisa Kudrow will be cast as Penny's mother. (Not true; CBS announced in July 2016 that Katey Sagal has been cast as her mother, Susan, and will be seen in the Season 10 premiere.)
- Penny makes a smart decision and tells Leonard that they could get married. Penny also proposes for them to elope to Vegas when they can't get around to setting a wedding date.
- By the end of the eighth season, Howard is the only guy who hasn't seen Penny naked, though he saw her topless when viewing her movie "Serial Ape-ist".
- Leonard had prepared vows for their wedding ceremony; however, Penny winged it with "You've Got a Friend in Me".
- Penny owned a pet pig called Moondance which lived happily on the farm in Nebraska until Wyatt drove a tractor and rotivator over it.
- Penny was one of the gang that married Howard and Bernadette while Bernadette married Leonard and Penny at their wedding redo ceremony.
- Bernadette, Raj, Leonard and Penny are the only characters of the social group/main cast whose parents have both been seen on-camera - Sheldon's father died when Sheldon was a child, Howard's father abandoned him and his mother when Howard was eleven, Stuart's mother and father have been mentioned and are both alive, Emily's father has been mentioned and it is not known if he is dead or alive and there has been no appearance or mention of Amy's father, Emily's mother, Leslie's mother or father to date.
- According to a July 2016 article posted on the TBBT Facebook page, we will meet Penny's mother and brother in the Season 10 premiere. Her mother, Susan, will be played by actress Katey Sagal (who played Kaley Cuoco's mother on 8 Simple Rules), while her brother, Randall, will be played by actor Jack McBrayer (30 Rock). According to the article, Susan is "stressed out and neurotic from a life dealing with her troubled—yet cheerful—son," who, as has been mentioned numerous times, is a drug dealer and ex-con.
- There has been no mention or showing of Penny's college education since "The Relationship Diremption". It's also unclear if she ever finished at all after re-enrolling in Season 6.
- In "The Platonic Permutation, Leonard read Penny's journal and revealed everything in it that he learned about her:
- Penny's birthday is December 2nd.
- When Penny was growing up she had a dog named Pepper.
- The street that Penny's family house and farm was on was Perkins Street.
- The last four digits of Penny's Social Security Number are 7, 6, 2, 1.
- Penny's favorite Spice Girl was Baby Spice.
- Penny's favorite *NSYNC band member was Justin.
- Penny did not have a favorite member of the Backstreet Boys because she loved *NSYNC.
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