Leslie: Wow. So, I heard your relationship with Penny crashed to the ground like blue ice falling out of an airplane lavatory.
Leonard: Where did you hear that?
Leslie: Actually I read it. Wolowitz texted me.
Leonard: (Reading the text) "Like blue ice falling out of an airplane lavatory." Yep.
Leslie: I thought it was a pretty good one, I gave him an L-O-L.

Leslie: PMS? It's a couple of days early, but
Leonard: No, it stands for Perpetual Motion Squad.
Leslie: Oh, right, of course, what was I thinking?

Howard: We'll just have to face Sheldon mano y mano y mano a mano.
Leslie: Wait, you're going up against Sheldon Cooper?
Howard: Yes!
Leslie: That arrogant, misogynistic, East Texas doorknob that told me I should abandon my work with high-energy particles for laundry and child bearing?
Leonard: She's in!

Leslie: There's no reason to feel uncomfortable just because we've seen each other's faces and naked bodies contorted in the sweet agony of coitus. Rest assured that any aspects of our sexual relationship regarding your preferences, your idiosyncrasies, your performance, are still protected by the inherent confidentiality of the bedroom.

Leslie: Come for the breasts, stay for the brains!

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.

Leslie: Just so we're clear, you understand that me hanging back to practise with you is a pretext for letting you know that I'm sexually available.
Leonard: Really?
Leslie: Yeah, I'm good to go.
Leonard: I thought you weren't interested in me.
Leslie: That was before I saw you handling that beautiful piece of wood between your legs.
Leonard: You mean my cello?
Leslie: No, I mean the obvious crude double entendre. I'm seducing you.

Leslie: Listen Leonard, neither of us are neuro-scientists, but we both understand the bio-chemistry of sex, ... I mean: Dopamine in our brain is released across synapses causing pleasure. You stick electrodes in a rat's brain, give him an orgasm button and he'll push that thing 'till he starves to death.
Leonard: Who wouldn't?

Leslie: Oh, Leonard, you magnificent beast.

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.