Sheldon: I'm a superior genetic mutation, an improvement on the existing mediocre stock.
Missy: And what do you mean "mediocre stock"?!
Sheldon: That would be you.

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.

Rajesh: Missy. Do you enjoy pajamas?
Missy: I guess.
Rajesh: Yes, well, we Indians invented them. You're welcome.
Howard: Yeah, well my people invented circumcision. You're welcome.

Howard: Well, she's free to examine my briefs.
Leonard: Howard!
Howard: I know! I'm disgusting. I should be punished. By her. Oh, look I did it again.

Sheldon: Eat this slice of cheese without farting and you can sleep with my sister.