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.

Penny: At one point, they had me figure out how to get a banana out of a puzzle box.
Leonard: Wait, Sheldon gave me a banana in a box. He was testing me, too.
Penny: Unbelievable.
Leonard: And how could a chimp even solve that? That was impossible.
Penny: Really? You couldn't get it out?

Leonard: If I take it off, Sheldon wins.
Penny: Sweetie, every night you don't kill him in his sleep, he wins.

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

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?

Howard: Enough with the guilt, ma. We'll still see each other. I'll come over every night and have dinner with you.
Mrs. Wolowitz The hell you will! What am I running here, a fancy restaurant? Does this look like the Olive Garden?