Wolowitz: Over the years, we've formulated a number of theories about how he might reproduce. I'm an advocate of mitosis.
Penny: I'm sorry?
Wolowitz: I believe one day Sheldon will eat an enormous amount of Thai food and split into two Sheldons.
Leonard: On the other hand, I think Sheldon might be the larval form of his species and someday he'll spin a cocoon and emerge two months later with moth wings and an exoskeleton

Leonard: Just apologize to him, okay?
Penny: What? I'm not going to apologize to that nut-case.
Leonard: Come on, it's easy. He'll even tell you what to say

Penny: Wait, Sheldon. This has gotten way out of hand. Okay, I've done some stupid things; you've done some stupid things. How about we just call it even and move on with our lives?
Sheldon: I've done no stupid things.
Penny: Look, you've got to meet me half way here.
Sheldon: I am meeting you half-way. I'm willing to concede that you've done some stupid things

Penny: I am going to introduce your friend to a world of hurt.
Leonard: You don't want to get into it with Sheldon. The guy is one lab accident away from being a super villain

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

Sheldon: I need to know exactly what Leonard did to get you to put an emotional cap in his buttocks.
Penny: What?
Sheldon: Again, urban slang, in which I'm beginning to get remarkable fluency

Penny: You don't always have to go along with what the woman wants.
Leonard: Huh.
Penny: What?
Leonard: Nothing... just re-thinking my whole life

Penny: Dave is not smarter than you, he's an idiot.
Leonard: Really? Why would you say that?
Penny: Because a smart guy takes the nude photos of his wife off his cell phone before he tries to take nude photos of his girlfriend.
Leonard: He tried to take nude photos of you?
Penny: That's what you took from that?

Penny: Wow, you've got a lot of money in there.
Sheldon: That's why it's guarded by snakes.

Penny: No, I can't. Sheldon, honey, I don't want things to be weird between us.
Sheldon: Won't it also be 'weird' if I have to say hello to you every morning on my way to work and you're living in a refrigerator box and washing your hair with rainwater?

Leonard: What was the plan?
Penny: Um, waitress for six months and then become a movie star.
Leonard: Was there a Plan B?
Penny: TV star.

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

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