Sheldon: Penny, while I subscribe to the "Many Worlds" theory which posits the existence of an infinite number of Sheldons in an infinite number of universes, I assure you that in none of them am I dancing.
Penny: Are you fun in any of them?
Sheldon: The math would suggest that in a few I'm a clown made of candy. But I don't dance.

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.

Penny: I give up. He's impossible.
Sheldon: I can't be impossible; I exist. I think what you meant to say is, 'I give up; he's improbable'.

Sheldon: You know, I've always wanted to go to a goth nightclub.
Howard: Really?
Sheldon: Bazinga! You never see any of my practical jokes coming, do you?

Leonard: I'm just saying, you catch more flies with honey than with vinegar.
Sheldon: You catch even more with manure, what's your point?