Raj: Come on, Sheldon, the world is filled with people doing things outside. Let's go outside. Outside is good.
Sheldon: If outside is so good, why has mankind spent thousands of years trying to perfect inside?

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.

Raj: You can't wear the hands on the date.
Sheldon: Hulk sad!

Penny: You know, I believe in ghosts, too.
Leonard: Great.
Penny: And astrology.
Leonard: I know, and pyramid power and healing crystals.
Penny: Oh, no, no, no, crystals don’t work.
Leonard: Really, that’s the line? Psychics are real, but crystals are voodoo?
Penny: Oh, Voodoo is real. You don't want to mess with Voodoo.

Leonard: How can I go out with a woman who believes in psychics?
Howard: Hey, I once dated a girl who believed she was abducted by aliens.
Leonard: And that didn't bother you?
Howard: Au contraire. It meant that she was gullible and open to a little probing.