Leonard: Just hiding some stuff in your closet, don't tell Penny.

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.

Sheldon: Oh, I don't mind, I'm very good at complaining. If it were an Olympic sport, I'd complain about what a stupid sport it is and then I'd take home the gold.

Leonard: Superman's gone. My stormtrooper's gone.
Sheldon: Your Klingon word-of-the-day calendar's gone.
Leonard: I'd say "damn it" in Klingon, but that wasn't until next month.
Sheldon: It's "khoo-vakh".
Leonard: Khoo-vakh!

Leonard: Sheldon, this is not a big deal. It's a little white lie, everyone does it.
Raj: Not me, I'm a 100% honest in all of my relationships.
Howard: And how single are you right now?
Raj: Eating-cake-on-the-toilet single.