Sheldon: I know mother, but you're not fooling me. Every time you want to talk it means you want me listen.
Mrs. Cooper: Then stop talking.
Sheldon: Yes, Ma'am.

Raj: I don't like bugs, okay. They freak me out.
Sheldon: Interesting. You're afraid of insects and women. Ladybugs must render you catatonic.

Sheldon: Scissors cuts paper, paper covers rock, rock crushes lizard, lizard poisons Spock, Spock smashes scissors, scissors decapitates lizard, lizard eats paper, paper disproves Spock, Spock vaporizes rock, and as it always has, rock crushes scissors.

Sheldon: Why are you crying?
Penny: Because I'm stupid.
Sheldon: That's no reason to cry. One cries because one is sad. For example, I cry because others are stupid, and that makes me sad.

Mary Cooper: Now, when you said on the phone he broke up with a girl, you meant an actual girl? Not something you kids whipped up in a lab?

Howard: On the potty, what are you five?
Raj: It's a potty, what do you call it?
Howard: A toilet.
Raj: That's a little vulgar for the dinner table, don't you think?
Howard: And potty is okay?
Raj: Potty is innocent. Potty is adorable.
Howard: What do you do on the potty, wee-wee?
Raj: If I don't have to boom-boom.

Sheldon: I'd like you to meet Oppenheimer, Frisch, Panofsky, Feynman, Weisskopf.
Mary: Yeah, I get it. You got a lot of cats, and you gave 'em cute Jewish names.