Penny: Ok, here's the deal. You either help me throw Leonard a birthday party or, so help me God, I will go into your bedroom and I will unbag all of your most valuable mint condition comic books. And on one of them, you won't know which, I'll draw a tiny happy face.
Sheldon: You can't do that. If you make a mark on a mint comic book, it's no longer mint.
Penny: Sheldon, do you understand the concept of blackmail?

Sheldon: Woman, you are playing with forces beyond your ken.
Penny: Yeah, well your Ken can kiss my Barbie.

Raj: [to Amy] If you were having Sheldon's baby, would you really want him in the room?
Penny: Yeah, if he's in the room when they're making the baby, I'll give you $10.

Penny: I mean, who even reads Scientific American?
Leonard: It's kind of a big deal.
Penny: If it's such a big deal, how come the biggest celebrity they could get for the cover is a molecule?

Howard: Try telling him it's a non-optional social convention.
Penny: What?
Howard: Just do it!
Penny: It's a non-optional social convention.
Sheldon: Oh, fair enough.
Howard: He came with a manual.

Sheldon: What computer do you have? And please don't say a white one.

Store Clerk: Excuse me, Sir, you don't work here.
Sheldon: Yes, well apparently neither does anyone else.