Leonard: Why can't you sleep?
Sheldon: Who knows? I haven't watched any scary movies recently. I'm no longer obsessing over why the predicted mass of the quantum vacuum has little effect on the expansion of the universe. And it's been weeks since I took that accidental sip of Red Bull.

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.

Wolowitz: But you love that spot.
Sheldon: No, I love my mother. My feelings for my spot are much greater.

Penny: OK Sheldon, what can I get ya?
Sheldon: Alcohol.
Penny: Could you be a little more specific?
Sheldon: Ethyl alcohol, 40 millilitres.

Penny: Sheldon, you can't re-program people.
Sheldon: No, you can't re-program people.