The Big Bang Theory — Season 4

Sept 201021m

Penny tags along on Sheldon's first ever date; Wolowitz finds a new use for a robotic arm.

Sept 201021m

Realizing he will not live long enough to download his consciousness into a robot body, Sheldon tries to extend his life span.

Oct 201021m

The guys are concerned as Sheldon searches for an alternative to human companionship.

Oct 201020m

An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work.

Oct 201021m

Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.

Oct 201022m

Leonard keeps an affair a secret from Sheldon, Howard and Raj.

Nov 201021m

Sheldon's answers during an FBI interview put Wolowitz's security clearance in jeopardy.

Nov 201019m

While the guys camp in line for a long-awaited movie screening, Penny and Bernadette invite Amy to her first slumber party.

Nov 201021m

Penny asks Leonard to lie to her father, while Howard, Raj and Bernadette pull an all-nighter at a telescope.

Dec 201020m

Amy finds she has sexual feelings for Penny's ex, while Koothrappali and Wolowitz try to prove who would be the better superhero.

Dec 201020m

The guys find a "super" use for Penny's new boyfriend, Zack, when they enter a costume contest as the Justice League.

Jan 201121m

Leonard's idea for a smartphone app derails his friendship with Sheldon.

Jan 201121m

Bernadette runs into her ex-boyfriend while attending a science event with Wolowitz.

Feb 201121m

Hoping it will make him a better teacher, Sheldon has Penny give him acting lessons. Raj has fantasies about a friend's girlfriend.

Feb 201120m

A wealthy donor to the university makes Leonard consider how far he's willing to go for the sake of science.

Feb 201120m

As Wolowitz contemplates taking things with Bernadette to the next level, Leonard rekindles his relationship with Raj's sister.

Feb 201121m

Sheldon becomes concerned when everybody begins to hang out at Raj's apartment and discovers Leonard is the center of the group.

Mar 201121m

Sheldon is baffled by Wolowitz's magic trick. Meanwhile, Leonard realizes dating Priya may make it impossible to continue being friends with Penny.

Mar 201121m

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.

Apr 201121m

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.

Apr 201121m

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.

May 201121m

Raj attempts to cure his social anxiety disorder while Penny uses Bernadette to spy on Leonard and his girlfriend.

May 201120m

When Howard finally breaks the news to his mom that he's engaged to Bernadette, it lands her in the hospital.

May 201121m

When Bernadette receives her PhD, Wolowitz feels emasculated. Raj and Leonard swap places and Penny does something she's regrets.