Leonard: Can I have a napkin.
Sheldon: I'm sorry, no!
Leonard: But you have a whole bunch of napkins.
Sheldon: Yes, I've moved to a four napkin system, lap, hands, face, and personal emergency. If you like, starting tomorrow, I'll add a guest napkin but I'm afraid there's nothing I can do for you today.
*Leonard grabs a napkin.*
Sheldon: Good luck, that's the face napkin.

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.

Bernadette: Does your mother call you every day at work to see if you had a healthy lunch?
Howard: My mother calls me every day at work to see if I had a healthy bowel movement.

Wil Wheaton: Game over, Moonpie.

Wil Wheaton: Did that guy just say "Revenge is a dish best served cold" to me in Klingon?