Raj: Please, Sheldon, I'm a young, virile visitor from a foreign land and I need to strut my stuff.
Sheldon: Let me offer you a compromise. Sometimes when I feel stifled and want a change of scenery, I use my imagination.
Raj: Oh, boy.
Sheldon: One of my favorite places to visit is the two-dimensional world described in Edwin Abbott's mathematical fantasy, Flatland.
Raj: I don't want to go to Flatland.
Sheldon: You're only saying that because you haven't been there. I am now a hexagon in two-dimensional space and can only perceive the edges of other objects.
Raj: Oy.
Sheldon: Is that you, Raj? I don't recognize your edge.

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.