This is a list of episodes for the third season of the American sitcom that was originally aired on CBS from September 21, 2009 to May 24, 2010 with 23 episodes. It has received higher ratings than the previous two seasons with over 15 million viewers. The Complete Third Season DVD erroneously credits Mark Cendrowski for directing the entire season.
- Main article: List of The Big Bang Theory characters
- Sheldon Cooper, Ph.D., portrayed by Jim Parsons, is a theoretical physicist. Originally from East Texas, he was a child prodigy, starting college at the age of 11, right after completing the fifth grade. He has an IQ of 187 and exhibits a strict adherence to routine; a lack of understanding of irony, sarcasm and humor; and a complete lack of humility. Sheldon gets introduced to Amy Farrah Fowler in the last scene of season three.
- Leonard Hofstadter, Ph.D., portrayed by Johnny Galecki, is an experimental physicist with an IQ of 173 who received his Ph.D when he was 24 years old. He shares an apartment with colleague and friend Sheldon Cooper and is the straight man of the series. Leonard and Penny date for most of the season and then break up.
- Penny, portrayed by Kaley Cuoco, is the attractive, blonde neighbor who lives across the hall in Apartment 4B from Sheldon and Leonard. She has aspirations of a career in show business, and has been to casting calls and auditions but has not been successful thus far. To pay the bills, she works as a waitress at The Cheesecake Factory. Her last name has never been revealed. She dated Leonard for most of the season. Penny starts to date Leonard because she misses him when he is gone all summer.
- Howard Wolowitz, M.Eng., portrayed by Simon Helberg, works as an aerospace engineer. He is Jewish, and lives with his mother. Unlike Sheldon, Leonard, and Raj, Howard lacks a Ph.D. He defends this by pointing out that he has a master's degree in engineering from the Massachusetts Institute of Technology and the apparatus he designs are actually built and launched into space, unlike the purely abstract work of his friends. He provides outrageous pick-up lines and fancies himself a ladies man with suitably unimpressed reactions from Penny; however, he has limited success with other women. Howard starts to date a friend of Penny's: Bernadette Rostenkowski.
- Rajesh Koothrappali, Ph.D., portrayed by Kunal Nayyar, originally comes from New Delhi, India. Known commonly as "Raj", he works as a particle astrophysicist at Caltech. He is very shy around women and is physically unable to talk to them unless he drinks alcohol. However, he has much better luck with women as opposed to his overly confident best friend Howard.
|Episode (Series)||Episode (Season)||Title||Original Air Date||Directed By||Description|
|41||1||The Electric Can Opener Fluctuation||September 21, 2009||Mark Cendrowski||Following the gang's return from the Arctic, Penny is happier than most and shows how much she cares about Leonard. Sheldon is devastated when he learns that the gang faked his experiment results.|
|42||2||The Jiminy Conjecture||September 28, 2009||Mark Cendrowski||The episode begins with Sheldon, Howard and Raj in the comic book store, the first two arguing about comics. Leonard arrives and the others are surprised he is not with Penny. As Wolowitz and Koothrappali pry a little more, they discover Leonard is not as happy with the sex.|
|43||3||The Gothowitz Deviation||October 5, 2009||Mark Cendrowski||After a sexual encounter that results in Penny's bed breaking, Penny and Leonard end up sleeping in Leonard's room, much to Sheldon's dismay. Raj and Howard go to a goth bar to meet girls.|
|44||4||The Pirate Solution||October 12, 2009||Mark Cendrowski||Raj must find a new job or be sent back to India. Sheldon has a solution, which is to allow Raj to work "for" him, rather than work "with" him. Raj reluctantly accepts the offer. With Raj working for Sheldon, it makes Howard lonely, so he tries to stay with Leonard and Penny.|
|45||5||The Creepy Candy Coating Corollary||October 19, 2009||Mark Cendrowski||Sheldon enters a trading-card competition upon learning that Wil Wheaton, who he hates for not coming to a sci-fi convention he went to, will also be attending. Howard has a blind date with a cute girl named Bernadette.|
|46||6||The Cornhusker Vortex||November 2, 2009||Mark Cendrowski||Sheldon, who grew up in Texas where it was popular, teaches Leonard how to understand football so that he can try to fit in with Penny's friends. During the game Leonard attempts to demonstrate what he has learned, but his explanations are too clinical, and he fails to fit in.|
|47||7||The Guitarist Amplification||November 9, 2009||Mark Cendrowski||An argument between Leonard and Penny proves "inconvenient" to Sheldon. We learn that Sheldon's parents argued a lot when he was growing up, and he doesn't like to hear people arguing at all.|
|48||8||The Adhesive Duck Deficiency||November 16, 2009||Mark Cendrowski||Leonard is with Rajesh and Howard on a camping trip to watch the Leonid Meteor Shower, but all three succumb to 'magic' cookies they get from Deadhead campers nearby. Sheldon comes to Penny's rescue when she slips in the tub and hurts her shoulder.|
|49||9||The Vengeance Formulation||November 23, 2009||Mark Cendrowski||Wolowitz's new girlfriend, Bernadette, asks him where their relationship is going after their third date. He avoids her for a week, thinking about whether he should "settle" for her or hold out for the impossible (a hot girl from a sci-fi series being interested in him).|
|50||10||The Gorilla Experiment||December 7, 2009||Mark Cendrowski||Bernadette, in the guy's apartment for dinner, shows an interest in physics, particularly in the work that Leonard is conducting. Leonard offers her the chance to watch him conduct an experiment at work. Wolowitz is jealous of this and accuses Leonard of being interested in Bernadette. Noticing Bernadette's attention, Penny asks Sheldon to teach her a little physics.|
|51||11||The Maternal Congruence||December 14, 2009||Mark Cendrowski||A visit from Leonard's mother, Dr. Beverly Hofstadter (Christine Baranski), delights Sheldon and horrifies Leonard. Penny is upset because Leonard didn't mention his mother's visit to her.|
|52||12||The Psychic Vortex||January 11, 2010||Mark Cendrowski||Sheldon and Koothrappali attend a university mixer. They meet Abby (Danica McKellar), who takes a liking to Raj, and her friend Martha (Jen Drohan), who they go on a couple of dates with. Leonard has troubling dealing with Penny believing in psychics.|
|53||13||The Bozeman Reaction||January 18, 2010||Mark Cendrowski||When their apartment is robbed and their TV, video games, and computers are stolen, Leonard and Sheldon turn to Howard to create a state-of-the-art security system, which includes an electrified net over the door. Sheldon gets caught in that net and decides he needs to leave Pasadena.|
|54||14||The Einstein Approximation||February 1, 2010||Mark Cendrowski||Sheldon's search for the answer to a physics problem keeps him up all night for several days and he becomes obsessed with finding the answer.|
|55||15||The Large Hadron Collision||February 8, 2010||Mark Cendrowski||Leonard announces that the professor who was invited to a trip to see CERN's Large Hadron Collider in Switzerland was unable to go, so he (Leonard) was designated to be the replacement to go to Switzerland, and he gets to take one guest with him. Sheldon assumes that he is going.|
|56||16||The Excelsior Acquisition||March 1, 2010||Peter Chakos||Sheldon misses his chance to meet comic book legend Stan Lee when he has to attend traffic court after receiving a ticket because of Penny. The ticket was a camera shot of Sheldon running a red light in Penny's car when he was taking her to the hospital in 'The Adhesive Duck Deficiency'.|
|57||17||The Precious Fragmentation||March 8, 2010||Mark Cendrowski||On the way to buy Chinese food, the guys see someone that looks like Adam West, and follow him to a garage sale, where they buy a box of merchandise for 60 dollars. They ignore Penny's anger at not getting food, and among other things they find a 'Lord of the Rings' ring.|
|58||18||The Pants Alternative||March 22, 2010||Mark Cendrowski||Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.|
|59||19||The Wheaton Recurrence||April 12 2010||Mark Cendrowski||One night after making love, Leonard surprises Penny by saying "I Love You" but she can only say "thank you" and they both start to think about where their relationship is heading. The next day, Penny and the guys are in a bowling match with Stuart and the gang from the comic book store.|
|60||20||The Spaghetti Catalyst||May 3, 2010||Anthony Rich||Leonard and Penny have broken up. Sheldon meets Penny in the hall and invites himself to visit her in an hour for spaghetti with hot dogs.|
|61||21||The Plimpton Stimulation||May 10, 2010||Mark Cendrowski||Dr. Elizabeth Plimpton (Judy Greer), a cosmological physicist from Princeton University, is a guest of Sheldon, but ends up sleeping with Leonard and Raj. Penny shows her jealousy.|
|62||22||The Staircase Implementation||May 17, 2010||Mark Cendrowski||Leonard tells Penny the story of how he first met Sheldon and how the elevator was broken. This episode is mostly in flashback.|
|63||23||The Lunar Excitation||May 24, 2010||Peter Chakos||The guys invite Penny to witness an experiment to bounce a laser off the moon and back to Earth. They meet her dim-witted friend Zack, which drives Penny to drink. She seeks comfort with Leonard. Raj and Howard sign up Sheldon for on-line dating and they match him with Dr. Amy Farrah Fowler.|