Boy, you'd think you could trust a horde of Hungarian barbarians

Penny: What's AFK?
Sheldon: Away From Keyboard.
Penny: Oh, I see.
Sheldon: What does that stand for?

Penny: Oh, my God, a treasure chest. I'm rich!
Sheldon: Level 3 and she thinks she's rich, what a noob.

Sheldon: You're asking me to keep a secret?
Penny: Yeah.
Sheldon: Well, I'm sorry, but you would have had to express that desire before revealing the secret, so that I could choose whether or not I wanted to accept the covenant of secret-keeping. You can't impose a secret on an ex post facto basis.
Penny: What?
Sheldon: Secret-keeping is a complicated endeavor. One has to be concerned not only about what one says, but about facial expressions, autonomic reflexes. When I try to deceive, I myself have more nervous tics then a Lyme disease research facility.... It's a joke. It relies on the homonymic relationship between "tick," the bloodsucking arachnid, and "tic," the involuntary muscular contraction. I made it up myself

Sheldon: So, you're saying that friendship contains within it an inherent obligation to maintain confidences?
Penny: Well, yeah.
Sheldon: Interesting. One more question—and perhaps I should have led with this—when did we become friends?

Penny: So it's fine with you if I'm not smart.
Leonard: Absolutely. [Penny closes the door on him] Okay, this time I know where I went wrong

Penny: Has [Leonard] ever been involved with someone who wasn't a brainiac?
Sheldon: Oh, well, a few years ago, he did go out with someone who had a Ph.D. in French Literature.
Penny: How is that not a brainiac?
Sheldon: Well, for one thing, she was French. For another, it was literature

Penny [referring to Sheldon]: What's up with Ichabod?
Leonard: Oh, he's trying to make a new friend
Penny: Well good for him
Leonard: Unless he makes one out of wood like Geppetto, I don't think it's going to happen

Penny: Yes, I will go out with you.
Leonard: Really?
Penny: Yeah. Why not? I mean, what do I have to lose?
Leonard: Yeah. That's the spirit

Penny: Leonard isn't the kind of guy I usually go out with.
Sheldon: Leonard isn't the kind of guy anyone usually goes out with

Leonard: What happened?
Penny: Well, I went over to Mike's to make up with him.
Leonard: Yeah. No, I know that part.
Penny: But he had already moved on.
Leonard: Already? That was quick.
Penny [crying]: That's what I said to the woman who had her legs wrapped around his neck!

Penny: I swear to God, I am done with guys like that. You know, macho with the perfect body and hair, and money.
Leonard: Yeah, that must get old quick

TBBT Quotes

Raj: Well, to paraphrase Shakespeare: It's better to have loved and lost than to stay home every night and download increasingly shameful pornography.
Penny: Oh... you poor baby.
Raj: What's wrong with me, Penny?
Penny: Nothing, nothing. You know, if we weren't friends - and you hadn't brought up that creepy pornography story - I'd be on you like the speed of light squared on matter to make energy.
Raj: Hey, you totally got that right. E = MC squared.
Penny: I listen. I have no idea what it means, but I listen.

Mrs. Cooper: Shelly! I'm so glad you're here!
Sheldon: I saw you having naked sex.