The Big Bang Theory

On the fourth season premiere, Penny (series star KALEY CUOCO) finds herself along for the ride on Sheldon's (series star JIM PARSONS) first date ever. Meanwhile, Wolowitz (series star SIMON HELBERG) finds a new use for a robotic arm. MAYIM BIALIK guest stars as Sheldon's date, Amy Fowler.

When Sheldon realizes he won't live long enough to download his consciousness into a robot body, he attempts to extend his lifespan. Apple Co-Founder STEVE WOZNIAK guest stars as Himself.

The guys are concerned as Sheldon searches for an alternative to human companionship after he and Amy (MAYIM BIALIK) break up. LAURIE METCALF reprises her role as Sheldon's mother.

An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work. Battlestar Galactica's KATEE SACKHOFF and Star Trek's GEORGE TAKEI guest star as themselves as Wolowitz's love gurus. MELISSA RAUCH reprises her role as Howard's girlfriend, Bernadette.

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

A visit from Raj's sister (guest star AARTI MANKAD) creates tension among the guys - especially when Leonard keeps an affair secret from Sheldon, Howard and Raj.

When an FBI agent (guest star ELIZA DUSHKU) interviews the guys for Wolowitz's security clearance, Sheldon's answers during the screening, put Wolowitz's clearance in jeopardy.

When the guys camp in line for a screening, their plans are thwarted by Sheldon's greatest nemesis, WIL WHEATON (guest starring as himself). Meanwhile, Penny and Bernadette invite Amy to her first slumber party.

Penny asks Leonard to lie to her father, Wyatt (guest star KEITH CARRADINE), while Howard, Raj and Bernadette pull an all-nighter at a telescope.

Amy finds she has sexual feelings for Penny's ex, Zack (guest star BRIAN THOMAS SMITH) while Koothrappali and Wolowitz try to prove who would be the better superhero.

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

Leonard's idea for a smartphone app derails his friendship with Sheldon as they fight for control of the project.

Tension runs high when everyone is staying at the same hotel for a science event and Bernadette runs into her ex-boyfriend (guest star RICK FOX, three-time NBA champion with the Los Angeles Lakers).

Sheldon wants Penny to give him acting lessons, hoping that they will help him become a better teacher. Meanwhile, Koothrappali fantasizes about his best friend's girlfriend.

A wealthy donor to the university makes Leonard consider how far he's willing to go for the sake of science. JESSICA WALTER (Arrested Development) guest stars as the widowed benefactress and JOSHUA MALINA (The West Wing) guest stars as the University President.

As Wolowitz contemplates taking things with Bernadette to the next level, he must choose between his girlfriend and his mother. Meanwhile, Leonard rekindles his relationship with Raj's sister, Priya.

When the gang starts hanging out at Raj's and Sheldon realizes it's actually Leonard who is the center of their social group, Sheldon decides to get a new group of friends.

Leonard must choose between his new girlfriend, Priya, and his friendship with Penny. Meanwhile, Howard drives Sheldon crazy with a magic trick.

When someone hacks Sheldon's online gaming account, the guys go on a quest to find the culprit.

Sheldon and Amy experiment on their friends by spreading gossip, while Howard takes a big step in his relationship with Bernadette.

Priya uses her lawyer skills to pick apart the roommate agreement…and put Sheldon in his place. Meanwhile, the girls take Sheldon dancing.

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

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

When Bernadette receives her Ph.D., the guys take joy in reminding an emasculated Wolowitz that he is the only one in their group who isn't a doctor. Meanwhile, Koothrappali becomes Sheldon's new roommate after hearing Leonard and Priya engaging in a Star Trek bedroom fantasy, on the fourth season finale.