Leonard: You know what, I'm so tired I can't even think straight. I'm going home. Will one of you guys give this nutbag a ride back later?
Sheldon: You can't go home. You have to take me to the dentist at four o'clock.
Leonard: Oh, can't you take the bus to the dentist?
Sheldon: Of course I can. It's coming back under the residual effects of the anesthesia, that's the problem. Two years ago after a deep gum cleaning, I thought I got on a bus but somehow wound up on a booze cruise to Mexico.
Raj: They put you under for a cleaning?
Sheldon: Yeah, they have to, I'm a biter.

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.

Sheldon: I would have been here sooner but the bus kept stopping for other people to get on it.

Leonard: You call that a glow stick? *Pulls out a Lightsaber* That is a glow stick!

Penny: Sheldon, that's not what girlfriends are for. Although you don't use them for what they're for, so what do I know?