Leonard: What are you doing in there?
Sheldon: I'm making hydrogen sulphide and ammonia gas. Just a little experiment in pest control.
Raj: It's not gonna work, dude. I grew up in India, an entire subcontinent where cows walk in the street, and nobody has ever had a solid bowel movement.
Sheldon: Well, we'll just see how long you can hold out.
Raj: Well, we'll just see how your noxious gas fares against my cinnamon-apple-scented aroma therapy candles.
Leonard: Didn't you say you're making hydrogen sulphide gas?
Sheldon: Yes.
Leonard: Isn't that flammable?
Sheldon: Highly. Oh, dear. [explosion]

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.

Leonard: Sometimes your movements are so lifelike I forget you are not a real boy.

Raj: Oh, you're so arrogant. If you were a super hero your name would be Captain Arrogant. And do you know what your super power would be? Arrogance.

Sheldon: Oh, Penny. Penny.
Penny: What's up?
Sheldon: Nothing. I just wanted to make Raj stop talking.