The Big Bang Theory

Howard uses a robotic arm for his own pleasure. Sheldon goes on a date with Amy Farrah Fowler, his first date ever, and Penny finds herself accompanying them.

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.

Sheldon breaks up with Amy Farrah Fowler, and the guys worry when he starts replacing her with cats.

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.

Sheldon meets Amy Farrah Fowler's mother and comes to the realisation he no longer wants to see Amy, and Leonard realises everyone is in a relationship except for him.

When Raj's sister has a one-day layover, he forbids the others from hooking up with her, unaware she and Leonard already did long ago.

The rest of the gang is interviewed by the FBI for Wolowitz's security clearance with Sheldon accidentally letting slip some damaging information.

The guys camp out in line to see a print of Raiders of the Lost Ark with 21 extra seconds and are outraged to see Wil Wheaton and his friends being allowed to skip the line. Penny and Bernadette invite Amy to their girls night.

Penny asks Leonard to lie to her visiting father, while Howard, Raj and Bernadette spend all night looking through a telescope.

Amy crushes on one of Penny's dim ex-boyfriends, Zack. Raj and Wolowitz argue over who'd 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.

Their friendship becomes strained when Sheldon tries to take over Leonard's creation of a smartphone application that solves differential equations.

Howard is jealous when Bernadette runs into her old boyfriend at a science event they're attending.

Sheldon wants acting lessons from Penny, hoping they will make him a better teacher.

After meeting at a fundraising gala, an aged but wealthy Caltech donor makes Leonard ponder if he's willing to have sex with her to secure another donation.

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.

Sheldon is in a crisis when he realises he's not the epicentre of the group, so he decides to find new friends.

Leonard has a tough choice to make when Priya asks him to stop spending time with Penny, forcing him to choose between the two women, and Howard keeps pestering Sheldon with a magic trick.

The guys become sleuths to find out who hacked Sheldon's online-game account.

Sheldon and Amy decide to start rumours about themselves as a social test. Meanwhile, Howard takes his relationship with Bernadette to an even higher level.

Priya uses her legal expertise to rip apart Sheldon's roommate agreement, and the women take the flustered Sheldon out dancing.

Raj makes an attempt to cure his phobia of talking to women, and Penny spies on Leonard and Priya with the help of Bernadette.

Mrs Wolowitz ends up in the hospital after Howard tells her he's marrying Bernadette. While there, Leonard stresses over Penny and Priya warming up to one another.

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.