The Big Bang Theory Season 4 Ratings

Penny ends up tagging along on Sheldon's first ever date with Amy, while Howard finds an unusual use for a robotic arm.

When Sheldon calculates the technology to download his consciousness into a robot won't be invented soon enough, he desperately tries to find a way to increase his lifespan.

Following his 'breakup' with Amy, the gang become concerned with Sheldon's obsessive search for non-human companionship and call his mother to intervene.

Howard tries to get Penny's help in winning back Bernadette, but first has to confess the embarrassing reason why they broke up in the first place. Raj and Sheldon clash over a desk.

Sheldon is scared that he is in a relationship when Amy asks him to meet her mother, and Leonard asks Howard and Bernadette to set him up because he is the only person in the group without a girlfriend.

Leonard tries to keep everyone from finding out that he spent the night with Raj's sister, but Sheldon finds out and concocts an elaborate story to help him keep the secret from Raj.

An FBI agent interviews the guys when Howard needs to obtain a security clearance.

The guys camp out all night waiting to see an extended cut of Indiana Jones, while Amy joins in on girls' night with Penny and Bernadette.

Penny asks Leonard to pose as her boyfriend when her father visits. Howard, Raj and Bernadette have an awkward encounter when they spend the evening together.

Amy discovers some unusual feelings and urges when she meets Penny's ex-boyfriend, Zack. Meanwhile, Howard and Raj argue over who would be a superhero and who would be their sidekick.

The guys enter a costume contest as members of the Justice League and convince Penny and Zack to join them.

Leonard has an idea for a new smartphone app and asks the guys for help, however Sheldon tries to take over the project, and Leonard fires him.

Chaos ensues when the gang spend the weekend together at a science convention.

To improve his skills as an instructor, Sheldon asks Penny to give him acting lessons. Meanwhile, Raj begins having impure fantasies about Bernadette.

To secure needed funding for the university, Sheldon convinces Leonard to get friendly with a wealthy benefactor.

Bernadette makes Howard choose between herself and his mother, while Penny and Raj become upset when Priya returns to town and resumes her relationship with Leonard.

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

Priya forces Leonard to choose between a relationship with her or a friendship with Penny. A magic trick by Howard has Sheldon fooled.

The guys go all out to help Sheldon find the person responsible for hacking his online gaming account, while the girls' hatred for Priya increases.

Sheldon and Amy secretly experiment on the gang by spreading rumors when they hear that Bernadette is thinking about breaking up with Howard.

When Priya finds a loophole in the roommate agreement to throw Sheldon out for the night, Penny, Amy and Bernadette take him to a nightclub.

Sheldon invents a three-player chess game, Penny and Amy use Bernadette to spy on Leonard and Priya, and Raj tries a new drug to treat his social anxiety.

Howard believes that his mom suffered a heart attack because he told her that he's marrying Bernadette, Sheldon freaks out over germs, and Penny and Priya compare notes on Leonard.

Raj moves in with Sheldon after hearing Leonard and Priya engage in a Star Trek fantasy in his apartment. Bernadette receives her doctorate.