Leonard: It's kinda like the Loch Ness Monster. Maybe there's something there, maybe there isn't. We'll never know but sometimes it's fun to creep yourself out thinking about it.

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.

(Howard has just told Mary about his upcoming trip to the International Space Station.)
Mary Cooper: I bet your mom is really proud of you.
Howard: Nope. She says if I don't back out, she's gonna go on a hunger strike. It'd take years before she'd be in any kind of danger, but still.

Mary Cooper: It's all themed. There's Jonah and the Whale Watching. All-you-can-eat Last Supper Buffet. And my personal favorite, Gunning with God.

Mary Cooper: I thought it was our Indians that had the occasional alcohol problem.
Leonard: We don't say that either. I'll make you list.
Mary Cooper: Oh, that'd be mighty white of you.