Leonard: I mean, I'm a perfectly nice guy. There's no reason we couldn't go to the restaurant and have a lovely dinner. Maybe take a walk afterwards, talk about things we have in common, "you love pottery? I love pottery!" You know, there's a pause, we both know what's happening. I lean in, we kiss, it's a little tentative at first but then I realise, she's kissing me back, and she's biting my lower lip. You know, she wants me, this thing is going the distance, we're going to have sex! Oh God! Oh, my God!

Leonard: Give me the phone.
Sheldon: But I thought you wanted to cancel?
Leonard: I can't because if I don't show up she'll still be expecting you.
Sheldon: Why would she be expecting me?
Leonard: Stop asking me all these questions, I need to take another shower.

Penny: So, what's new in the world of physics?
Leonard: Nothing.
Penny: Really, nothing?
Leonard: Well, with the exception of string theory, not much has happened since the 1930s. And you can't prove string theory, at best you can say “Hey, look, my idea has an internal logical consistency.”
Penny: Ah. Well I'm sure things will pick up.

Penny: Leonard?
Leonard: Yeah.
Penny: Was this supposed to be a date?
Leonard: This? No. No, of course not, this was just you and me hanging out with a bunch of guys who didn't show up, because of work and a colonoscopy.
Penny: Okay, I was just checking.
Leonard: When I take a girl out on a date, and I do, she knows she’s been dated. Capital D. Bold face, underline, like Day-ted.
I think I might have a little concussion, I'm going to go lay down for a while. Good night.

Penny: Leonard, I didn't know you played the cello?
Leonard: Yeah, my parents felt that naming me Leonard and putting me in advanced placement classes wasn't getting me beaten up enough.

Leslie: Is it the waitress?
Leonard: Penny? What about her?
Leslie: Well, I thought I saw your pupils dilate when you looked at her, which, unless you're a heroin addict, points to sexual attraction.

Sheldon: Alright, I'm moving my infantry division, augmented by a battalion of Orcs from Lord of the Rings, we flank the Tennessee Volunteers, and the North once again wins the Battle of Gettysburg.
Howard: Not so fast, remember the South still has two infantry divisions, plus Superman and Godzilla.
Leonard: No, no, no, no, Orcs are magic, Superman is vulnerable to magic, not to mention, you already lost Godzilla to the Illinois Cavalry and Hulk.
Raj: Why don't you just have Robert E. Lee charge the line with Shiva and Ganesh?

Penny: So, do you know who's in there?
Sheldon: Well, there's Leonard. ... (Picking up violin case) And he's either with Leslie Winkle or a 1930s gangster.

Leonard: Thank you. What did she mean, "she's happy for me"? Is she happy because I'm seeing someone or is she happy because she thinks that I'm happy? Because anyone who cared for someone would want them to be happy, even if the reason for their happiness made the first person unhappy. You know, because the second person, though happy, is now romantically unavailable to the first person.

Leslie: Uh, what are you doing?
Leonard: Just extending the intimacy. Do you want to slip over to the radiation lab and share a decontamination shower?
Leslie: Okay, uh, what exactly do you think's going on between us?
Leonard: I'm not sure, but I think I'm about to discover how the banana felt.

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.

Leonard: Well what did she mean by that? Was that just a generic platitude or was that a subtle bid for attention?
Sheldon: You know why this hamburger surpasses the Big Boy? This is a single decker hamburger whereas the Big Boy is a double decker. This has a much more satisfying meat to bun to condiment ratio.
Leonard: Are you even listening to me?
Sheldon: Of course I'm listening. Blah blah, hopeless Penny delusion, blah blah blah.

(Raj introducing his friends to his parents on video chat)
Leonard: Hi!
Raj: And over here is Sheldon.
Sheldon: Hi.
Raj: He lives with Leonard.
Mrs. Koothrappali: Oh, that's nice. Like Haroun and Tanweer.
Raj: No, no, not like Haroun and Tanweer.

Dr. Koothrappali: So, are you boys academics like our son?
Guys: Yes.
Dr. Koothrappali: And your parents are comfortable with your limited earning potential?
Guys: Not at all.
Raj: Papa, please don't start.
Dr. Koothrappali: God, its just a question, hes so sensitive.

Leonard: Dr. and Mrs. Koothrappali, in all fairness, it wasn't entirely Rajs fault.
Dr. Koothrappali: This is a family matter Sheldon.
Leonard: No, I'm Leonard.
Dr. Koothrappali: Oh, sorry, you all look alike to us.