Leonard: I'm just saying, you catch more flies with honey than with vinegar.
Sheldon: You catch even more with manure, what's your point?

How on earth can you say "dirty sock" and "relax" in the same sentence?

Sheldon

I don't object to the concept of a deity, but I'm baffled by the notion of one that takes attendance

Amy

Howard wanted to write "mumbo jumbo," but I said no, our Sheldon would say "hokum."

Raj

That's not afternoon. That's prevening.

Sheldon

When you say mistake, do you mean a fortunate mistake like the discovery of penicillin?

Leonard

Sheldon: Hello, Amy Farrah Fowler. I'm sorry to inform you that you've been taken in by unsupportable mathematics designed to prey upon the gullible and the lonely. Additionally, I am being blackmailed with a hidden dirty sock.
Amy: If that was slang, I'm unfamiliar with it. If it was literal, I share your aversion to soiled hosiery.

Wolowitz: Okay, what if I were to tell you, tomorrow at 4:30, you could meet a woman who has been scientifically chosen to be your perfect mate?
Sheldon: I would snort with derision and throw my arms in the air, exhausted by your constant tomfoolery.

Incidentally, one can get beaten up in school simply by referring to oneself as one.

Sheldon

Yes, in 1917 when Albert Einstein established the theoretic foundation for the laser in his paper "Zur Quantentheorie der Strahlung," his fondest hope was that the resultant device be bitchin'.

Sheldon

Sheldon: As a native Texan, I must say that I've never heard the phrase "yee haw" used in quite that context.
Penny: Oh God.
Sheldon: "Oh God." That I've heard on multiple occasions.

I'm telling you, dude. The only way to feel better about Penny going out with other guys is for you to get back on the whores.

Raj

The Big Bang Theory Season 3 Quotes

Sheldon: Why are you crying?
Penny: Because I'm stupid!
Sheldon: Well that's no reason to cry; one cries because one is sad. For example, I cry because others are stupid and it makes me sad.

Penny: I give up, he's impossible
Sheldon: I can't be impossible, I exist. I believe what you meant to say is, "I give up, he's improbable."