Leonard: If you don't like this Christy, why are you letting her stay?
Penny: Well, she was engaged to my cousin while she was sleeping with my brother, so she's kind of family

Leonard: What's wrong?
Penny: Well, Howard and Christy are kind of hooking up in my bedroom.
Leonard: Are you sure?
Penny: Look, I grew up on a farm. From what I heard, they're either having sex, or Howard's caught in a milking machine

Wolowitz: Oh, by the way, where did you get that loofah mitt? Yours reaches places that mine just won't?
Penny: You used my loofah?
Wolowitz: More precisely, we used your loofah. I exfoliated her brains out!

Leonard: Can't you see that she's using you?
Wolowitz: Who cares? Last night she pulled off her blouse and I wept.
Penny: Look, Howard, I know her, okay. She'll sleep with anyone as long as they keep buying her things.
Wolowitz: Really?
Penny: Yeah.
Wolowitz: Yay

Penny: Hey, if you guys need a fourth, I'll play.
Leonard: Great idea!
Sheldon: Uh, no. The wheel was a great idea. Relativity was a great idea. This is a notion, and a rather sucky one at that.
Penny: Why?!
Sheldon: Why? Oho, Penny, Penny, Penny.
Penny: Oho, what, what, what? [picks up controller]
Sheldon: This is a complex battle simulation with a steep learning curve. There are a myriad of weapons, vehicles, and strategies to master, and not to mention an extremely intricate back story.
Penny: Oh, cool! Whose head did I just blow off?
Sheldon: Mine.

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?

Raj [drunk]: Where did my life go, Penny?
[everyone is shocked Raj is talking to Penny]
Raj: One day, I'm a carefree bachelor, and the next, I'm married and driving a minivan to pee-wee cricket matches in suburban New Delhi.
Penny: Are you talking to me?
Raj: Is there another Penny here?

Penny: I need some guinea pigs.
Sheldon: Okay, there's a lab animal supply company in Reseda you can try. But if your research is going to have human applications, may I suggest white mice? Their brain chemistry is far closer to ours.
Penny: I swear to God, Sheldon, one day I'm going to get the hang of talking to you.
Leonard: His mom's been saying that for years

Sheldon: When I was a little boy and got sick, which was most of the time, my mother would read [The Monkey and the Princess] to me. It's about an Indian princess who befriends a monkey who was mocked by all the other monkeys because he was different. For some reason I related to it quite strongly.
Penny: I know the reason.
Leonard: We all know the reason

Penny [to Raj about Lalita]: No one can make you get married. Why don't you just meet this girl and see what happens?
Raj: Haven't you been listening to me? I cannot talk to women!
Leonard: Um, Raj?
Wolowitz: No, no, let's see how long it takes him

Leonard [referring to Sheldon singing]: What got into him?
Penny: Oh, just a couple virgin Cuba Libres that turned out to be kinda slutty

Penny: I'm a Sagittarius, which probably tells you way more than you need to know.
Sheldon: Yes, it tells us that you participate in the mass cultural delusion that the sun's apparent position relative to arbitrarily defined constellations at the time of your birth somehow affects your personality.
Penny: Participate in the what?

TBBT Quotes

Oh, Bernadette, please play my clarinet.

Raj's poem

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?