Leonard: What if you could make Kripke look even sillier than he made you look?
Raj: I don't think that's possible, dude.
Leonard: You're not helping.
Raj: I didn't come here to help, I came here to mock.

Sheldon (to himself): Structure, constant structure, one atom.
Howard: Boy, he's really gone, isn't he?
Leonard: Yeah, this morning he used a stick of butter as deodorant.
Howard: I thought I smelled popcorn.

Raj: Okay, show of hands: who's up for this?
(Howard eagerly raises his hand)
Leonard: We'll all be naked, in front of each other.
Howard (lowering his hand): I'm out.

Howard: Are you planning on kidnapping a woman?
Sheldon: Sarcasm?
Howard: Yes, but mixed with genuine concern.

(Sheldon notices Penny taking Leonard to his bedroom)
Sheldon: What's going on?
Penny: Get your noise-cancelling headphones, 'cause it's gonna get loud.
Sheldon: Oh, not this again.

Leonard: Not only that Sheldon saved my life, but that he didn't report me to the landlord, or the police, or homeland security.

Sheldon: This is the temperature you agreed to in the roommate agreement.
Leonard: Aw, screw the roommate agreement!
Sheldon: No, you don't screw the roommate agreement. The roommate agreement screws you.

Leonard: You know what, go to Hell and set their thermostat.
Sheldon: I don't have to go to Hell. At 73 degrees, I'm there already!

Wolowitz: Good God, what have we done?

Sheldon: As a native Texan, I must say I've never heard the phrase "yeeehaw" used in quite that context.

Penny: Damn you, you rat bastard! In the olden days, I never would have known he was that stupid.

Raj: The Good Wife is on. I tell you, this is my new Grey's Anatomy.

Leonard: Relax, it's just a dirty sock.
Sheldon: How on earth can you say "dirty sock" and "relax" in the same sentence?

Sheldon: Hello, Amy Farrah Fowler. I'm sorry to inform you that you've been taken in by unsupportable mathematics designed to prey upon the gullible and the lonely. Additionally, I am being blackmailed with a hidden dirty sock.
Amy: If that was slang, I'm unfamiliar with it. If it was literal, I share your aversion to soiled hosiery.

Sheldon: Incidentally, one can get beaten up in school simply by referring to oneself as one.