Leonard: Ethyl alcohol inhibits electrical conduction in the nerve cells and stimulates re-uptake receptors of inhibitory neurotransmitters like gamma-amino butyric acid.

Leonard:What am I supposed to say? Sure, Penny, I'm cool with having your old boyfriend sleep in your apartment.
Leonard imitating Penny: Well, Leonard, it doesn't matter if you're cool or not, 'cause I'm penny and I'm pretty and I can do whatever the hell I want.

Leonard: How about that, Einstein was wrong.
Penny: What?
Leonard: Approaching the speed of light doesn't slow down time, approaching them does.

Leonard: Thanks for closed captioning my pain, Raj.

Sheldon: Everyone at the university knows I eat breakfast at 8:00 and move my bowels at 8:20.
Leonard: Yes, how did we live before Twitter?

Leonard: If he were any bigger, he'd have moons orbiting him.
Sheldon: Oh, snap.

Wolowitz (watching America's Next Top Model): Oh, look! That's the future Mrs. Wolowitz. No, wait! That's the future Mrs. Wolowitz. With her head in the lap of... what a coincidence... it's the future Mrs. Wolowitz.
Leonard: Yeah, and they can all move in with you and your mother. The current Mrs. Wolowitz.

Penny: Ok, here you go Leonard. One tequila sunrise!
Leonard: Thank you! You know, this drink is a wonderful example of how liquids with different specific gravities interact in a cylindrical container!

Sheldon: You know, this situation with Koothrappali brings to mind a story from my childhood.
Howard: Oh, goody, more tales from the Panhandle.
Sheldon: That's Northwest Texas. I'm from East Texas, the Gulf region. Home to many Vietnamese shrimpers.
Leonard: Do the shrimpers feature in your story?
Sheldon: No. Anyway, when I was eight, a Montgomery Ward delivery van ran over our family cat, Lucky.
Howard: Lucky?
Sheldon: Yes, Lucky.
Leonard: He's irony-impaired. Just move on.
Howard: Ok, dead cat named Lucky. Continue.

Leonard: You shush. I'm happy. I want to talk about it.

Kurt: Where's your back up?
Leonard: I don't need back up, I have right on my side ... and I'm wearing cargo shorts under my pants.

Sheldon: This is an auspicious moment, like Robert Oppenhiemer or Neil Armstrong, we need the appropriate words to mark this historic scientific event.
Rajesh: How about, die toaster, die!
Leonard: That'll do it!

Howard: Behold the Mobile Omni-Directional Neutralization and Termination Eradicator! Or...
Leonard, Sheldon, Howard, Raj: Monte.

Leonard: Why are you learning Chinese?
Sheldon: I believe the Szechuan Palace has been passing off orange chicken as tangerine chicken, and I intend to confront them.
Leonard: If I were you, I'd be more concerned about what they're passing off as chicken.

Leonard: (To Howard and Raj) Sheldon is at the Cheesecake Factory.
Leonard: (On the phone to Penny) Just tell him to go home.
Penny: Well, he won't leave. He says he's afraid he'll pass out on the bus and someone will harvest his organs.
Leonard: (to Howard & Raj) He is paranoid and he has established a nest.