Episode 1
The Robotic Manipulation
Penny tags along on Sheldon's first ever date; Wolowitz finds a new use for a robotic arm.
Season 4
This season the Big Bang gang’s romantic universe expands. On the rebound from Penny, Leonard falls into the arms of Raj’s sister Priya. Sheldon gets a girlfriend, or rather a friend who is a girl: Amy, a dour neurobiologist who declares herself besties with Penny. Howard and Bernadette heat up. And so do Raj and Bernadette (at least in Raj’s Bollywood daydream).
All Episodes
Episode 1
The Robotic Manipulation
September 23, 2010
Penny tags along on Sheldon's first ever date; Wolowitz finds a new use for a robotic arm.
Episode 2
The Cruciferous Vegetable Amplification
September 30, 2010
Realizing he will not live long enough to download his consciousness into a robot body, Sheldon tries to extend his life span.
Episode 3
The Zazzy Substitution
October 7, 2010
The guys are concerned as Sheldon searches for an alternative to human companionship.
Episode 4
The Hot Troll Deviation
October 14, 2010
An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work.
Episode 5
The Desperation Emanation
October 21, 2010
Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.
Episode 6
The Irish Pub Formulation
October 28, 2010
Leonard keeps an affair a secret from Sheldon, Howard and Raj.
Episode 7
The Apology Insufficiency
November 4, 2010
Sheldon's answers during an FBI interview put Wolowitz's security clearance in jeopardy.
Episode 8
The 21-Second Excitation
November 11, 2010
While the guys camp in line for a long-awaited movie screening, Penny and Bernadette invite Amy to her first slumber party.
Episode 9
The Boyfriend Complexity
November 18, 2010
Penny asks Leonard to lie to her father, while Howard, Raj and Bernadette pull an all-nighter at a telescope.
Episode 10
The Alien Parasite Hypothesis
December 9, 2010
Amy finds she has sexual feelings for Penny's ex, while Koothrappali and Wolowitz try to prove who would be the better superhero.
Episode 11
The Justice League Recombination
December 16, 2010
The guys find a "super" use for Penny's new boyfriend, Zack, when they enter a costume contest as the Justice League.
Episode 12
The Bus Pants Utilization
January 6, 2011
Leonard's idea for a smartphone app derails his friendship with Sheldon.
Episode 13
The Love Car Displacement
January 20, 2011
Bernadette runs into her ex-boyfriend while attending a science event with Wolowitz.
Episode 14
The Thespian Catalyst
February 3, 2011
Hoping it will make him a better teacher, Sheldon has Penny give him acting lessons. Raj has fantasies about a friend's girlfriend.
Episode 15
The Benefactor Factor
February 10, 2011
A wealthy donor to the university makes Leonard consider how far he's willing to go for the sake of science.
Episode 16
The Cohabitation Formulation
February 17, 2011
As Wolowitz contemplates taking things with Bernadette to the next level, Leonard rekindles his relationship with Raj's sister.
Episode 17
The Toast Derivation
February 24, 2011
Sheldon becomes concerned when everybody begins to hang out at Raj's apartment and discovers Leonard is the center of the group.
Episode 18
The Prestidigitation Approximation
March 10, 2011
Sheldon is baffled by Wolowitz's magic trick. Meanwhile, Leonard realizes dating Priya may make it impossible to continue being friends with Penny.
Episode 19
The Zarnecki Incursion
March 31, 2011
Sheldon's online-game account is hacked by Todd Zarnecki, who then proceeds to steal all his items prompting the guys to go on a quest to retrieve them. Penny, Bernadette and Amy discuss how Penny groomed Leonard to be willing to try various things and more adventurous boyfriend... for some other woman — Priya.
Episode 20
The Herb Garden Germination
April 7, 2011
Sheldon and Amy decide to start several rumors about the others as a test. Meanwhile, Howard takes his relationship with Bernadette to even higher level.
Episode 21
The Agreement Dissection
April 28, 2011
When Leonard spends too much time in the shower with Priya, Sheldon charges Leonard with two violations of the roommate agreement. However, before he can get too far, Priya uses her skills as a lawyer to nullify the charges due to the agreement's vague wording, much to Sheldon's dismay. When the guys take advantage of Priya's skills in order to eat Greek food on pizza night, Sheldon goes to Penny, who invites him to a girls' night out with Amy and Bernadette, which Sheldon agrees to after Penny mentions that they may be talking trash about Priya. After the girls drink some cocktails, they decide to take Sheldon dancing, which Sheldon reluctantly goes along with. After dancing, Sheldon takes an intoxicated Amy back to her apartment and as well as talking about Priya, meets a monkey who is addicted to smoking cigarettes. Amy tells Sheldon not to give in to Priya's law skills, before kissing him and going to her bathroom to vomit.
Episode 22
The Wildebeest Implementation
May 5, 2011
Raj attempts to cure his social anxiety disorder while Penny uses Bernadette to spy on Leonard and his girlfriend.
Episode 23
The Engagement Reaction
May 12, 2011
When Howard finally breaks the news to his mom that he's engaged to Bernadette, it lands her in the hospital.
Episode 24
The Roommate Transmogrification
May 19, 2011
When Bernadette receives her PhD, Wolowitz feels emasculated. Raj and Leonard swap places and Penny does something she's regrets.