Sheldon: This is how you're going to entertain your little cousin and his friends? By lying to them?
Howard: How is this lying?
Sheldon: A magic show is an inherently deceitful proposition. This is an ordinary top hat. You've chosen that card freely. I do not have a set of lock picks lodged in my keister.
Raj: Can't you just enjoy the wonder, Sheldon? Why must you peek behind the curtain? Or up the butt?
Sheldon: If we poison the critical thinking faculties of children by telling them that rabbits come out of hats, then we create adults who believe in astrology and homeopathy and that Ryan Reynolds was a better choice for Green Lantern than lovable rogue Nathan Fillion.

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.

Amy: Jewelry? Seriously? Sheldon, you are the most shallow, self-centered person I have ever met! Do you really think another transparently manipulative - Oh, it's a tiara! Put it on me, put it on me, put it on me, put it on me.

Penny: You look beautiful.
Amy: Of course I do, I'm a princess and this is my tiara!

Sheldon: Hard as this may be to believe, it's possible that I'm not boyfriend material.
Leonard: Glad I was sitting down for that.