Penny: Uh, hey, guys, guys, you will really appreciate this, I read the best science joke on the Internet. Alicia, you won't get it, but it's right up their alley. Anyway, so, this physicist goes into an ice cream parlor every week and orders an ice cream sundae for himself, and then offers one to the empty stool sitting next to him. This goes on for a while until the owner finally asks him what he's doing. The man says, "Well, I'm a physicist, and quantum mechanics teaches us that it is possible for the matter above this stool to spontaneously turn into a beautiful woman who might accept my offer and fall in love with me." The owner then says, "Well, lots of single, beautiful women come in here every day, why don't you buy an ice cream for one of them, and they might fall in love with you?" And the physicist says, "Yeah, but what are the odds of that happening?"
Leonard: It's a little insulting, don't you think?
Penny: How would I know? I'm not even sure I get it.

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?

Wolowitz: Penny, let me take this opportunity to point out that you are looking particularly ravishing today.
Penny: Not with a thousand condoms, Howard.
Wolowitz: So there is a number.

Penny: Leonard, and Howard, and Raj, they aren't like other guys. They're special.
Alicia: Okay, they're special, and?
Penny: Well let's see how can I explain this. Um. They don't know how to use their shields.
Alicia: Shields?
Penny: Yeah. You know like in Star Trek and you're in battle, and you raise the shields.
*Realizing what she said* Where the hell did that come from?

Sheldon: Please. We're facing a far more serious problem than stray arachnids.
Leonard: It's not so bad.
Sheldon: Not bad? It's horrible. You hear stories about this things, but you never think it'll happen to you.
Leonard:So they steamed your dumplings. Get over it.