Amy: You and I are in a relationship. I help you with your shortcomings, and you help me with mine.
Sheldon: How would you feel if I contacted your mother behind your back?
Amy: Delighted that you showed any interest in my family at all?
Sheldon: "Delighted"? What - Not if I guessed for a hundred years.

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: Well, uh, Howard and Bernadette had their baby.
Mary Cooper: (gasps) Oh, that's wonderful! Now, have they decided to raise it Jewish or regular?
Sheldon: Welcome to Texas.

Bernadette: Everyone's a better mom than me.
Raj: Oh, don't take it so personally, maybe your baby's just a jerk.

Mary Cooper: Sheldon, if you're trying to prove me wrong, the tighty-whities on your head ain't changing my mind.