Sheldon: I'm sorry, Leonard. This is Toby Loobenfeld. He's a research assistant in the particle physics lab, but he also minored in theater at MIT.
Toby: It was more of a double major actually. Theater and physics. You can guess which one my bourgeois parents pushed me towards.
Leonard: Yeah, I got it.

Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?

Howard: Don't feel bad. Some day someone will be throwing out your work, too.
Leonard: That someone was Sheldon and the day was yesterday.

Leonard: Well, you can spend the rest of the day being bitter about this--
Sheldon: Agreed.
Leonard: I was going to say "or," but why bother?

Sheldon: I am uncomfortable having been included in your lie to Penny.
Leonard: What was I supposed to say?
Sheldon: You could have told her the truth.
Leonard: I could not have said that, it would have hurt her feelings.
Sheldon: Is that a relevant factor?
Leonard: Yes.
Sheldon: Then I suppose you could have agreed to go.
Leonard: What would I have said afterwards?
Sheldon: I would suggest something along the lines of "singing is neither an appropriate vocation nor avocation for you and if you disagree, I recommend you do a CAT scan to locate the tumor which is pressing on the cognitive processing center of your brain".

Sheldon: Leonard?
Leonard: Yes?
Sheldon: (Sarcastic) When we played chess earlier, you were terrific, and I can't wait to play you again. Goodnight!

(Sheldon repeatedly knocking and saying Leonard's name)
Leonard: Ugh, this would be so much easier if I were a violent sociopath!