Leonard: Look, you do understand that Sheldon really doesn't care when he gets the money back. It's actually one of the few idiosyncrasies that doesn't make you want to, you know, kill him.

Leonard: Penny, as a scientist, my job is to figure out why things happen. But I don't think I'll ever understand how someone like me could get to be with someone like you. You know maybe I don't need to understand it, I just need to be grateful. I love you, Penny.

Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

Leonard: My point is, while you're spending all this time on your own, building computers or practicing your cello, what you're really doing is becoming interesting. When people finally do notice you, they're gonna find someone a lot cooler than they thought. And for those of you that were popular in high school, it's over, sorry. Thank you. Congratulations.

Leonard: OK, is everyone clear on the plan?
Howard: Yes, Koothrappali's going to wet himself, I'm gonna throw up, Sheldon's gonna run away and you're going to die. Shall we synchronize our watches?

Sheldon: There once was a brave lad named Leonard.
With a fi fi fiddle dee dee.
He faced a fearsome giant.
While Raj just wanted to pee.

Leonard: Sheldon, would you be prepared on a non-presidential basis, to create an emergency ad-hoc slurpee/icee equivalency?
Sheldon: Oh Leonard, you know I can't do that.