Sheldon: This car weighs, let's say, 4,000 pounds. Now add 140 for me, 120 for you...
Penny: 120?!
Sheldon: Oh, I'm sorry. Did I insult you? Is your body mass somehow tied into your self-worth?

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

Leonard: So, I've got a gunshot wound. That's pretty bad-ass.
Penny: No, you've got a Reebok with a gunshot wound and an ouchie on your pinky toe.

Sheldon: Yes, since their relationship became carnal, Penny has updated his designated term of endearment, distinguishing him from those she calls "sweetie," usually as an attempt to soften a thinly-veiled insult.
Penny: You're boring people, sweetie.
Sheldon: Although sometimes, she omits the veil entirely.

Penny: So, what do you guys do around here?
Sheldon: Well, today we tried masturbating for money

Leonard: No, just you and me.
Penny: Have you thought this through?
Leonard: Yes, and I think we should go anyway.

Leonard: This tray contains clues as to what you and I are going to be doing on Valentine's Day.
Penny: Wow okay, let's see. We got milk chocolate, Swiss cheese, fondue... my lactose intolerant boyfriend is going to eat all this and I'm going to climb on your back and rocket to the moon?

Bernadette: Doesn't he know you have a boyfriend?
Penny: Oh, she doesn't have a boyfriend; she has a Sheldon.

Penny: Sheldon, what do you want?
Sheldon: I'm certain this will come as no surprise to you, but Leonard is failing in yet another relationship.
Penny: He's having problems with Stephanie?
Sheldon: She's sending virtual livestock to random men on the Internet

Penny: What's the matter?
Sheldon [confused by Leonard having Leslie in his room]: I don't know what the protocol is here. Do I stay? Do I leave? Do I wait to greet them with a refreshing beverage?
Penny: Gee, Sheldon, you're asking the wrong girl. I'm usually on the other side of the tie.

Penny: Who's Adam West?
Sheldon: Who's Adam West!? Leonard, what do you talk about after the coitus?
Wolowitz: My guess is "four minutes, a new record!"

Leonard: I missed you.
Penny: You see me all the time. You sure you don't just miss the sex?
Leonard: Well, yeah, the sex with you is pretty great. Have you ever tried it?
Penny: I have. You're not wrong.

TBBT Quotes

Sheldon [to Kripke]: Also, I am given to understand that your mother is overweight.
Raj: Oh, snap.
Sheldon: Now of course, if that is the result of a glandular condition and not sloth and gluttony then I withdraw that comment.

How is "doable" anything but a compliment?

Wolowitz