The Big Bang Theory Season 3 Episode 11 - The Mate...
Leonard's mother (Christine Baranski) visits, which pleases Sheldon but upsets Leonard. .
The Big Bang Theory Season 3 Episode 7 - The Guita...
A squabble between Leonard and Penny sees Sheldon playing mediator, though out of his own incovenience from the sitiation rather than altruism.

The Big Bang Theory Season 3 Episode 3 - The Gotho...
Howard takes Raj along to check out the Goth dating scene. Sheldon uses chocolate as part of a behavior modification experiment on Penny.
The Big Bang Theory Season 2 Episode 19 - The Dead...
Penny feels threatened when another sexy woman moves into the apartment building.

The Big Bang Theory Season 2 Episode 18 - The Work...
Penny's business selling hair products out of her apartment gets out of hand when an over-caffeinated Sheldon takes charge.
The Big Bang Theory Season 2 Episode 17 - The Term...
The gang is thrilled when they learn Terminator: The Sarah Connor Chronicles' Summer Glau is also aboard their train to San Francisco.

The Big Bang Theory Season 2 Episode 16 - The Cush...
Paintball leads to a squabble between Sheldon and Penny, as well as romance between Howard and Leslie.
The Big Bang Theory Season 2 Episode 15 - The Mate...
Leonard suffers through a dreadful visit from his mother (Christine Baranski) that ends up bringing him and Penny closer.

The Big Bang Theory Season 2 Episode 14 - The Fina...
Sheldon helps Penny with a financial crisis, but his solution leads to a confrontation between Leonard and Penny's burly ex-boyfriend Kurt (Brian Patrick Wade).
The Big Bang Theory Season 2 Episode 13 - The Frie...
Sheldon creates a scientific procedure for making friends.

The Big Bang Theory Season 2 Episode 12 - The Kill...
Penny's criticism of Wolowitz's romantic life pushes him into depression and AWOL for a fighting robot battle the rest of guys are depending on him for.