The Big Bang Theory

The fifth season premiere picks up where the fourth season finale left off as the gang deals with the aftermath of Penny and Raj's night together. While Penny worries that she's screwed things up permanently with her friends, Sheldon takes command of the paintball team. Emmy® nominee CHRISTINE BARANSKI (The Good Wife) reprises her role as Leonard's emotionally distant mother.

A battle of wills between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya (recurring guest star AARTI MANN), who has moved back to India.

Leonard attends a co-worker's wedding as Amy's date. Meanwhile, Howard tries to convince Bernadette to live with his mom after they get married by suggesting a trial run with the two of them staying with his mom over the weekend.

When Raj is upset he's the only one of the four guys who is not in a relationship, Penny sets out to find the perfect date, introducing him to Emily (guest star KATIE LeCLERC -- Switched at Birth) a girl he can actually talk to!

Sheldon's old nemesis, WIL WHEATON (guest starring as Himself), returns and invites everyone to a housewarming party. Sheldon threatens to "defriend" Leonard if he attends. But when he hears that BRENT SPINER (guest starring as Himself), the actor who played Commander Data, will be there, Sheldon decides to go to the party after all... only to discover new levels of treachery. Meanwhile, Howard gets an out-of-this-world opportunity that Bernadette reacts to strongly.

Craving a little motherly love, Sheldon competes with the gang for his mother's attention when she comes to visit. LAURIE METCALF reprises her role as Sheldon's mother, Mary.

A cute comic book artist (guest star COURTNEY FORD) puts Leonard's relationship with Priya to the test; while Sheldon, getting into the spirit of Halloween, tries to scare the guys.

Amy is heartbroken when Bernadette and Penny go shopping for wedding dresses without her.

Can friends with benefits still be friends without? Leonard and Penny try hanging out alone, while Sheldon must overcome his fear of birds.

Sheldon becomes jealous and considers taking his relationship with Amy to the next level when Stuart (guest star KEVIN SUSSMAN) from the comic book store asks her out on a date.

Leonard must face his fears after being contacted by his high school tormentor (guest star LANCE BARBER), while Penny realizes that she might have been a bully herself.

Sheldon gets in trouble with Amy when he isn't impressed by her recent accomplishment, and it's up to Penny to teach him how to be a better boyfriend. Howard, meanwhile, must come to grips with Bernadette's dislike of children.

The possibility of Leonard and Penny getting back together could prove disastrous when Leonard offers Penny a spur of the moment invitation to a romantic dinner for two on the 100th episode of the series.

Leonard and Penny experiment with dating again by "beta testing" their relationship, while Raj develops a peculiar relationship with his phone's virtual assistant.

Sheldon's selfish demands force Leonard to reconsider their friendship. Could this be the end of The Roommate Agreement? Meanwhile, Howard tries to pick his astronaut nickname, but NASA astronaut MIKE MASSIMINO (guest starring as himself) has other ideas.

When Sheldon is forced to take a vacation by the university, he goes to work with Amy in her neurobiology lab. Meanwhile, Bernadette wants Howard to sign a pre-nuptial agreement.

When a corner office at the University opens up, Sheldon must compete for it with his office nemesis, Barry Kripke. Meanwhile, a personal gift from Amy makes Penny uncomfortable.

Sheldon's life is turned upside-down after his barber becomes hospitalized. Now, that there's been a change in his routine, Sheldon finds himself re-evaluating his entire life. Meanwhile, astronaut training causes Howard to rethink his decision to go into space.

It's on...like Alderaan, when the guys plan a weekend Star Wars gaming marathon! But when Sheldon chooses the guys-only weekend over a weekend with Amy to visit her aunt, he is destined to feel the force!

It's a dream come true for Sheldon when he has a close encounter with his hero, Mr. Spock. Legendary sci-fi icon LEONARD NIMOY guest stars, lending his voice to a unique reprisal of his three-time Emmy®-nominated Star Trek role.

When Wolowitz gets tow work with world-renowned scientist STEPHEN HAWKING (guest starring as Himself), Sheldon is willing to do anything to meet his hero.

Howard's wedding plans are in jeopardy after the guys (and Wil Wheaton) throw him a bachelor party. After details of his sexual history are leaked online, Bernadette reconsiders marrying Howard.

When NASA reschedules Howard's mission and puts his wedding plans in jeopardy, he's forced to face his fears and Bernadette's dad (guest star CASEY SANDER). Meanwhile, Leonard says something surprising to Penny in the bedroom.

Howard Wolowitz crosses over into the final frontiers of space...and marriage on the fifth season finale. When Howard and Bernadette decide they want to be married before his NASA space launch, the gang rushes to put on a wedding. NASA Astronaut Mike Massimino guest stars as Himself.