Alex: This conversation is making me uncomfortable.
Sheldon: Yeah, you and me both, sister. Now, please understand, I don't hold you responsible for your behavior because, see, from an evolutionary standpoint, you're a slave to your desire to reproduce. But during the work day, when you feel possessed by amorous intent, may I suggest that you suppress it by leafing through this illustrated book of sexually transmitted diseases? Let's see here. Oh, yes. Check out this oozy doozy.
Alex: I have to go.
Sheldon: So does this fellow, but he can't without it burning like hot soup.

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.

Amy: I have a lab full of coked up monkeys with nothing to lose.

Sheldon: My father used to say that a woman is like an egg salad sandwich on a warm Texas day.
Alex: What?
Sheldon: Full of eggs and only appealing for a short time.

Alex: Is there a problem?
Sheldon: Let's not call it a problem. Let's call it an opportunity. To solve a serious problem.