Sheldon: To really understand the story here, we need to start at the very beginning. A small town in East Texas where a young genuis named -
Leonard: - Sheldon!
Sheldon: Yes, that's right, Sheldon Cooper. He was bitten by his neighbor's dog, leading to his first scientific break through: the Doggy Death Ray. Which sadly he couldn't build because Santa wouldn't bring him enriched uranium.

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: Aww, Raj did the dishes.
Howard: How do you know I didn't do them?
Bernadette: Because once when all the knives were dirty, you cut a bagel with your keys.

Sheldon: No, that's okay. I can fight my own battles. Isn't that right, Bawwy?
Barry Kripke: Is that a reference to my speech impediment? That's pretty hurtful. I can't control it.
Sheldon: You're right. That was uncalled for. I take it back.
Barry Kripke: Of course you do, because you're The Retractor!

Penny: (To Raj's dog) Bark once if you need me to call PETA.