Leslie: Listen, Leonard, neither of us are neuroscientists but we both understand the biochemistry of sex. I mean, dopamine in our brains is released across synapses causing pleasure. You stick electrodes in a rat's brain, give him an orgasm button, he'll push that thing until he starves to death.
Leonard: Who wouldn't?
Leslie: Well, the only difference between us and a rat is that you can't stick an electrode in our hypothalamus. That's where you come in.
Leonard: Yeah, well, I'm just glad to be a part of it. So what happens now?
Leslie: Well, I don't know about your sex drive, but I'm probably good till New Years.

Sheldon: You know, we were annihilated by our own incompetence and the inability of some people to follow the chain of command.
Leonard: Sheldon, let it go.
Sheldon: No, I want to talk about the fact that Wolowitz shot me in the back.

Leonard: Okay, let me put it this way, I'm doing it.
Sheldon: You can't. I'm the lead author.
Leonard: Oh, come on. The only reason you're the lead author is because we went alphabetically.
Sheldon: I let you think we went alphabetically to spare you the humiliation of dealing with the fact that it was my idea. Not to put too fine a point on it, but I was throwing you a bone. You're welcome.

Leonard: Excuse me, I designed the experiment that proved the hypothesis.
Sheldon: It doesn't need proving.
Leonard: So the entire scientific community is just supposed to take your word?
Sheldon: They're not supposed to, but they should.

Sheldon: Were you trying to impress Penny?
Leonard: No, no not at all. ... A little bit.
Sheldon: How'd that work out for you?
Penny: (entering the apartment) Leonard, ready to go?
Sheldon: Libido 1, Truth 0.

Sheldon: As I have explained repeatedly, unlike you, I don't need validation from lesser minds. No offense.
Leonard: Really, so why did you come?
Sheldon: Because I knew you’d screw this up.
Leonard: I didn't screw it up.
Sheldon: Oh, please. I admit, that spherical chicken joke, that was hilarious. But it was straight downhill from there.

Leonard: See, the liquid metal Terminators were created in the future by Skynet, and Skynet was developed by Miles Dyson, but that future no longer exists due to Dyson's death in Terminator 2.
Sheldon: Okay, then riddle me this. Assuming all the good Terminators were originally evil Terminators created by Skynet but then reprogrammed by the future John Connor, why would Skynet, an artificial computer intelligence, bother to create a petite hot 17 year-old killer robot?
Leonard: Skynet is kinky? I don't know.
Sheldon: Artificial intelligences do not have teen fetishes.

Leonard: Do you have a cousin Leopold?
Sheldon: No, I made him up. I think you'd call him Lee.
Leonard: I don't get it. I already told her a lie. Why replace it with a different lie?
Sheldon: Well, first of all, your lie was laughably transparent, where mine is exquisitely convoluted. While you were sleeping I was weaving an un-unravelable web.
Leonard: un-unravelable?
Sheldon: Yes, if she Googles "Leopold Houston" she'll find a Facebook page, an online blog depicting his descent into drug use, and a desperate yet hopeful listing on e-Harmony.com.

Sheldon: (In Mandarin) Many oxen are in my bed! Many, many oxen!
*Chen flings his hands at Sheldon*
Sheldon: (Mandarin) Oy Vey.

Wolowitz: So, how'd it go with Leslie?
Leonard: Oh, we tried kissing, but the earth didn't move. I mean any more than the 383 miles it was gonna move anyway.

Raj: Hey, look, I found an iPod.
Howard: It's smashed beyond repair. What are you gonna do with it?
Raj: What else? Sell it on eBay as slightly used.

Leonard: (Talking about Raj to Penny) Don't you have a drink that could make him less obnoxious?
Penny: Drinks do not do that.

Mary Cooper: Now let's get crackin'. Shower. Shirt. Shoes. And let's shove off.

Penny: Anyway, I was talking to Leonard this morning and I think he feels really bad about it.
Sheldon: Huh.
Penny: Well, how do you feel?
Sheldon: I don't understand the question.
Penny: Well I'm just asking if it's difficult to be fighting with your best friend.
Sheldon: Oh. I hadn't thought about it like that. I wonder if I've been experiencing physiological manifestations of some sort of unconscious emotional turmoil.
Penny: Wait, what?
Sheldon: I couldn't poop this morning.

Leonard: How was Nebraska?
Penny: Oh, better than North Dakota! [silence] I guess that joke's only funny in Nebraska.
Sheldon: From the data at hand you really can't draw that conclusion. All you can say with absolute certainty is that that joke is not funny here.
Penny: Boy, it's good to be back.