Leonard: Nice to know everything's OK with your plumbing. Err, the building's plumbing.

Penny: (crying) How could he do that?
Leonard: Oh, you did throw an 80-gig iPod-- Yeah, no, how could he do that?

Leonard: (Helping Althea with the crossword puzzle) One across is Aegean, eight down is Nabokov, 26 across is MCM, fourteen down is-- move your finger, phylum, which makes 14 across Port-au-Prince. See, Papa Doc's capital idea, that's Port-au-Prince. Haiti.

Leonard: Open the landing bay doors, shuttle craft approaching.

Leonard: What do you mean it happened again?!

Leonard: Hypothetically, if I had access to a lieutenant Uhura uniform, would you wear it?
Priya: Leonard, it is a source of great pain to me and my family that my brother has that outfit in his wardrobe.

Sheldon: What did the toaster oven ever do to you?
Leonard: What did I do to Jimmy Mullins in the third grade? He still punched me in the face with my own fists. Sorry, you little nerd. You were just in the wrong boys' room at the wrong time.

Leonard: Okay, there are ogre tracks and a trail of broken candy canes in the snow. Sheldon, what do you do?
Sheldon: I signal my contempt for your cruel plan to shove Christmas joy down my throat by making a gesture that says get a load of this guy.

Sheldon: No I should apologize. I never realized to what extent our friendship was a burden to you.
Leonard: That is not fair. I complain about what a burden it is at least once a month.
Sheldon: No, no, no. Let's not sugarcoat this. You find me finnicky, pedantic and annoying.
Penny: No, he doesn't.
Leonard: I have actually used those exact words before. In that order.

Amy: I've never seen him (Sheldon) this happy before.
Leonard: That's because you've never seen him on "Restock the Medicine Cabinet" day.

Leonard: So when you say you're not going to flip out about the DVD, here's what that means. Don't fixate on it, or wake me up in the middle of the night, or nag me through the door while I'm on the toilet.

Raj: Do you support this?
Leonard: Of course I do. She's a great actress. I'm proud she's taking this risk.
Amy: That's nice.
Leonard: You bought that!? Great! I gotta call her before I forget how I said it.

Sheldon: Gentlemen, I am one step away from securing a huge guest for my convention.
Leonard: Does that step include chloroform and a roll of duct tape?

Raj: Does he sound like a criminal?
Howard: What do you mean?
Raj: You know, did he say things like "youse guys" or "listen here, say".
Leonard: Yes, he's late because he's on his way here from 1940.

Leonard: You're too close to it, but Amy has had a huge impact on your life.
Sheldon: You're right. Without realizing it, I have allowed that women to alter my personality.
Leonard: Sheldon, you didn't have a personality. You just had some shows you liked.