A Christmas visit from his mother has Leonard discovering she's kept a lot of news from him that she shares with Sheldon and worrying if she'll approve of his romance with Penny.
Penny seeks Sheldon's help to better comprehend Leonard's physics work. Wolowitz sees green when Leonard invites Bernadette to watch an experiment.
Barry Kripke embarrasses Sheldon on NPR, and the gang rallies to help him get his revenge. Wolowitz, desperate to keep his romance with Bernadette alive, gets advice from a fantasy version of Katee Sackhoff. Another source of The Big Bang Theory Season 3 Episode 09 - The Vengeance Formulation.
Leonard and Penny's first big fight sees Sheldon playing mediator due to childhood trauma that's left him with an inability to be around loud verbal conflicts.
Leonard, hoping to fit in with Penny's football-loving friends, gets tutored in the sport by Sheldon. Raj is infuriated when Wolowitz's skirt-chasing leads to the loss of his prized patang.
Sheldon looks forward to squaring off against the the one actor from the Star Trek universe he holds enmity towards—Wil Wheaton—in a fantasy collectable card game tournament. Wolowitz cashes in on an old pact with Leonard to get Penny to set him up with a friend of hers.
Facing a return to India, Raj needs a job desperately enough to consider working for Sheldon. Meanwhile, Howard becomes a third wheel to Leonard and Penny.
Howard takes Raj along to check out the Goth dating scene. Sheldon uses chocolate as part of a behavior modification experiment on Penny.
The guys' prestigious offer to work over the summer at the North Pole—and Penny's resultant behavior—leaves Leonard unsure if he should go.
Leonard is torn between being honest or self-serving when Stuart asks his advice for an upcoming second date with Penny. Wolowitz realizes there's a crucial error in a toilet he designed for the International Space Station.