The ninth season of The Big Bang Theory was confirmed on May 12, 2015, alongside seasons 8 and 10. It aired during the 2015-16 television season.
Season 9 premiered on Monday, September 21, 2015. First taping was on August 11, 2015.
- Johnny Galecki as Dr. Leonard Hofstadter (24/24)
- Jim Parsons as Dr. Sheldon Cooper (24/24)
- Kaley Cuoco as Penny Hofstadter (24/24)
- Simon Helberg as Howard Wolowitz (24/24)
- Kunal Nayyar as Dr. Rajesh Koothrappali (24/24)
- Mayim Bialik as Dr. Amy Farrah Fowler (24/24)
- Melissa Rauch as Dr. Bernadette Rostenkowski-Wolowitz (24/24)
- Kevin Sussman as Stuart Bloom (10/24) (Recurring & Main Cast)
- Laura Spencer as Dr. Emily Sweeney (5/24) (Recurring & Main Cast)
|Title||Original Air Date||Directed By||Description|
|184||01||The Matrimonial Momentum||September 21, 2015||Mark Cendrowski||Sheldon confronts Amy while watching Leonard and Penny march down the aisle, but has Penny gotten over Leonard's indiscretion?|
|185||02||The Separation Oscillation||September 28, 2015||Mark Cendrowski||Leonard dreams that Sheldon kissed Penny leading him to reconcile with her and Sheldon gives the newlyweds some tickets to San Francisco. Sheldon continues to lash out at Amy.|
|186||03||The Bachelor Party Corrosion||October 5, 2015||Mark Cendrowski||The girls throw Penny a bachelorette party, while the guys kidnap Leonard and take him to Mexico for a weekend celebration.|
|187||04||The 2003 Approximation||October 12, 2015||Mark Cendrowski||Leonard finally moves out while the other guys try to form a band. Sheldon looks for a new roommate.|
|188||05||The Perspiration Implementation||October 19, 2015||Mark Cendrowski||The guys decide to take up a sport, fencing, and the girls are helping Stuart get more female interest in the comic book store. Both Sheldon and Amy are thinking about dating others.|
|189||06||The Helium Insufficiency||October 26, 2015||Mark Cendrowski||While some Swedish scientists try to steal Leonard and Sheldon's superfluid theory, the rest of the gang work on getting Amy back into the dating world.|
|190||07||The Spock Resonance||November 5, 2015||Nikki Lorre||Wil Wheaton interviews Sheldon for a Star Trek documentary where he reveals the ring and his plan to propose to Amy. Bernadette wants to start renovating their house|
|191||08||The Mystery Date Observation||November 12, 2015||Mark Cendrowski||Amy has a formal date with Dave, which Penny, Leonard, and Bernadette secretly spy on. Sheldon has Howard and Raj help him find a new girlfriend since they found Amy for him.|
|192||09||The Platonic Permutation||November 19, 2015||Mark Cendrowski||Leonard and Penny cook their first Thanksgiving dinner together, Sheldon and Amy go to the aquarium together and the rest serve the homeless Thanksgiving dinner together.|
|193||10||The Earworm Reverberation||December 10, 2015||Mark Cendrowski||Amy invites Dave over to her apartment for a date and Sheldon can't get a tune out of his head. Howard and Raj track down the one fan for their band.|
|194||11||The Opening Night Excitation||December 17, 2015||Mark Cendrowski||As the guys prepare to go to the premiere of the new Star Wars movie, Sheldon plans a special gift for Amy's birthday.|
|195||12||The Sales Call Sublimation||January 7, 2016||Mark Cendrowski||Leonard goes with Penny on a sales call and meets a psychiatrist. Amy is away at a convention and Stuart moves out of the Wolowitz House.|
|196||13||The Empathy Optimization||January 14, 2016||Mark Cendrowski||Sheldon is impossible when he gets a cold and then based upon Amy's suggestion, he drives everyone crazy with his apologies. The guys want to take a road trip on a party bus to get away from him.|
|197||14||The Meemaw Materialization||February 4, 2016||Mark Cendrowski||Amy meets Sheldon's grandmother Meemaw who is not happy with her for having broken up with Sheldon though she does reveal to Amy that Sheldon does have a ring for her. Raj meets a sci-fi script writer who wants to work with him.|
|198||15||The Valentino Submergence||February 11, 2016||Mark Cendrowski||Amy and Sheldon host a live Sheldon Cooper Presents: Fun with Flags, Raj breaks up with Emily, Leonard and Penny go out on a teen date and the the Wolowitzes put in a hot tub and find a rabbit.|
|199||16||The Positive Negative Reaction||February 18, 2016||Mark Cendrowski||Bernadette tells Howard he his going to be a father which causes him all kinds of worries. The guys take Howard to a karaoke bar to celebrate, where he gets himself involved with Leonard and Sheldon's project.|
|200||17||The Celebration Experimentation||February 25, 2016||Mark Cendrowski||Amy wants to throw a birthday party for Sheldon who is put off because when he was young his sister told him Batman was coming and he didn't. The gang invites Adam West to the party.|
|201||18||The Application Deterioration||March 10, 2016||Mark Cendrowski||Sheldon works up contract to split their portion of their guidance system invention royalties, but Bernadette does not like how it's done. Raj must again decide between Emily and Claire when they both contact him.|
|202||19||The Solder Excursion Diversion||March 31, 2016||Mark Cendrowski||Howard and Leonard lie to their spouses about seeing a movie premiere, while Raj spills the beans about their lie. Sheldon and Amy go shopping for Sheldon's new laptop, but Sheldon reveals a secret to Amy.|
|203||20||The Big Bear Precipitation||April 7, 2016||Mark Cendrowski||Amy talks Sheldon into joining Leonard and Penny on their weekend in the woods. Penny admits that she isn't happy in her job. Meanwhile, Bernadette and Howard feel that Raj is interfering with the pregnancy.|
|204||21||The Viewing Party Combustion||April 21, 2016||Mark Cendrowski||At a "Game of Thrones" viewing party, everyone is fighting except Sheldon and Penny. Howard ends up in the hospital because Leonard made a snack with pistachios in it.|
|205||22||The Fermentation Bifurcation||April 28, 2016||Mark Cendrowski||When Leonard, Penny, Amy, Howard, Raj and Claire all go out to a wine tasting party and run into Zack. Bernadette and Sheldon spend the night together at Apartment 4A playing games.|
|206||23||The Line Substitution Solution||May 5, 2016||Anthony Rich||Sheldon hires Stuart to spend the day with Amy when he’d rather go to a movie screening. Also, Leonard’s mother, Beverly, comes to town and Penny struggles to make a connection with her even planning a redo of their wedding.|
|207||24||The Convergence-Convergence||May 12, 2016||Mark Cendrowski||The second wedding ceremony for Leonard and Penny is on while Beverly fights with her ex-husband Alfred who is invited and Mary Cooper takes an interest in Alfred. Also, Howard gets a message from the Air Force about his invention that stirs his paranoia.|
- This season had the same number of 24 episodes, adding the total amount of episodes for the entire series up to 207 and included the 200th episode. (Season Trend)
- A little of Amy's backstory was included this season.
- Leonard and Penny made it to a Las Vegas chapel and got married.
- Mary Cooper appeared in the premiere episode to give Sheldon advice and the truth about the ring was revealed - it belonged to Sheldon's great-grandmother (not his MeeMaw, so it's an old family heirloom) and Mary encouraged Sheldon to hold on to it just in case, and he did.
- Amy met some other guys and dated them after she broke up with Sheldon in Season 9 Premiere - she signed up to a dating app (without anyone else being aware of it, including Penny and Bernadette) and went on three different coffee dates, one of which included "Dave" played by British comedian, Stephen Merchant.
- Sheldon purchased tickets for Leonard and Penny as a wedding gift.
- The girl that Leonard kissed on the boat trip appeared in the 2nd episode of season 9. The girl is called Mandy and she was played by Melissa Tang.
- Penny's father Wyatt made an appearance in the third episode.
- There was a storyline focusing on the release of the new Star Wars movie: Star Wars Episode 7: The Force Awakens, which was The Opening Night Excitation.
- Barry Kripke appeared in episodes 5 "The Perspiration Implementation" and 6 "The Helium Insufficiency".
- Kripke and Stuart attempted to ask Amy out but she turned them both down.
- Kaley's hair grew longer throughout the season.
- Wil Wheaton returned in episode 7 "The Spock Resonance".
- Leonard Nimoy's son, Adam Nimoy made a guest appearance.
- Leonard and Penny found out about Sheldon's engagement ring and he admitted that he was planning to propose to Amy.
- Casey Sander returned as Bernadette's father, Mike.
- Howard and Bernadette finally had a serious talk about maybe starting a family.
- Emily Sweeney was promoted to regular during the fourth episode of season 9, and became a semi-regular like Stuart and not in every episode like Amy and Bernadette are.
- Mayim Bialik has hinted that things will start to develop for Sheldon and Amy now that Leonard and Penny know about the ring.
- Amy dumped Dave after it is revealed he was obsessed with Sheldon.
- Analeigh Tipton guest starred as Sheldon's date, Vanessa in episode 8. She was last seen in Season 2 but as a different character though.
- Simon Helberg has revealed he would like Howard's long-absent father to be introduced this season; Steven Molaro has hinted it is a possibility. This implies he might appear.
- Sheldon and Amy became friends again in episode 9.
- Amy wanted to be his girlfriend again, but Sheldon declined, saying that it was too hard getting over her.
- Bob Newhart made a reappearance as Arthur Jeffries AKA Professor Proton in episode 11. He appeared in his ghostly Jedi form to help Sheldon sort through his feelings and give him advice regarding an important decision. The release of this episode (17th December) also coincided with the release of the new Star Wars movie (the show's producers had previously revealed that there would be a Star Wars themed episode this season to celebrate the release of Star Wars: The Force Awakens.)
- Wil Wheaton reprised his role as himself once again in episode 11. He was last seen in episode 7 "The Spock Resonance".
- Sheldon and Amy reunited in episode 10 (the 4-year anniversary of "The Flaming Spittoon Acquisition" when he asked her to be his girlfriend). They shared a very passionate kiss and proclaimed their love for each other.
- Sheldon and Amy finally consummated their relationship after Sheldon decided to spend the night with her instead of going to the new Star Wars movie premiere on Amy's birthday.
- No Christmas episodes aired in 2015 which is the first time since season 5.
- Sheldon's Meemaw finally got introduced this season. She was played by actress June Squibb.
- Meemaw initially disapproved of Amy's relationship with Sheldon because of their breakup but when Sheldon defends Amy, she then gives them her blessing. She also reveals to Amy that Sheldon has the ring, first shown in the Season 8 finale.
- Raj met a new potential love interest, a scriptwriter for a sci fi children's show called Claire. She was played by Alessandra Torresani.
- Raj broke up with Emily, but then a few episodes later they hooked up ("The Application Deterioration").
- Bernadette was revealed to be pregnant ("The Valentino Submergence").
- Claire got into a relationship with her 'ex-boyfriend' then broke up with him again, leading to being turned down after Raj asked her out.
- Penny and Leonard discussed the possibility of having children one day, and the two agreed but they didn't decide yet for when to get pregnant.
- Christine Baranski, Sara Gilbert, John Ross Bowie and Wil Wheaton reprised their respective roles in the 200th episode. Adam West and Professor Stephen Hawking also guest starred.
- Sheldon's birthday was finally celebrated in the 200th episode, "The Celebration Experimentation".
- Leonard's father was finally introduced in the last episode and is played by "Taxi" and "Numb3rs" star Judd Hirsch.
- Penny was set to make another career move. She will quit her sales rep job but she won't return to acting.
- Zack Johnson returned this season in "The Fermentation Bifurcation".
- Kripke appears in 4 episodes this season, the most out of all his appearances within the series.
- Beverly Hofstadter and Mary Cooper reprised their roles in "The Convergence-Convergence".