The Big Bang Theory

Sheldon flees back to Texas in disgrace when he learns that the guys tampered with his arctic expedition data -- threatening Leonard's hopes for a romantic encounter with Penny.

Leonard and Penny struggle to recover from an awkward first hookup, while Sheldon and Howard (SIMON HELBERG) stake their best comic books on a bet to determine an insect species.

Sheldon uses science to try to change Penny's behavior.

Raj must find a new job or be sent back to India.

While Sheldon settles a score with his nemesis, Star Trek's WIL WHEATON (guest starring as himself), Wolowitz begs Leonard to get Penny to set him up with one of her friends

Leonard learns about football from an unlikely tutor.

Leonard and Penny's argument proves inconvenient to Sheldon.

Sheldon must come to Penny's rescue.

After he's humiliated on NPR, Sheldon vows to destroy Kripke, while, Wolowitz tries not to destroy his new relationship with Bernadette. KATEE SACKHOFF guest stars.

Sheldon takes on his greatest challenge when he attempts to help Penny understand physics, and Wolowitz becomes jealous when Leonard starts hanging out with his new girlfriend.

Will Leonard's relationship survive a visit from his mother?

While Sheldon and Koothrappali attend a university mixer, Leonard is upset to discover that Penny believes in psychics. DANICA McKELLAR stars as the object of Raj's attraction.

Sheldon struggles to cope after his apartment is robbed.

Sheldon has a case of "Physicist's Block."

Leonard must choose between Sheldon and Penny when he can bring only one guest on a trip to see the world's largest and highest energy particle accelerator in Switzerland.

Sheldon misses a chance to meet comics legend STAN LEE.

The guys must choose between a movie prop and their friendship.

Sheldon gets a bad case of stage fright.

Sheldon faces off with Star Trek's Wil Wheaton again.

Sheldon is caught in a lie, trying to please Leonard & Penny.

JUDY GREER guest stars as a famous female physicist.

Leonard remembers the day he moved in with Sheldon.

Penny has a night of angry, drunken sex with Leonard, much to his confusion. Meanwhile, Howard and Raj search for Sheldon's perfect match online.