Raj: Maybe moving in was a bad idea. I haven't been here one day, I'm already causing problems.
Penny: You didn't do anything. It's Sheldon.
Leonard: "You didn't do anything.It's Sheldon." That'd make a nice needlepoint pillow.

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.

Raj: I'm sorry, guys. Sheldon was upset, Leonard and Penny were fighting. I just wanted to go someplace where I wasn't causing problems.
Howard: (sighs) I'll say it again. India.

Sheldon: What if she's correct? Doesn't that say something troubling about us?
Amy: I don't know. I just think you're the kind of person who likes a contingency plan.
Sheldon: That is true. Did you know I figured out in which order I would eat all my friends in the event of an apocalypse?
Amy: You need to stop hanging out with your brain so much. It's not a good influence.

Penny: Well, it's like that science thing. For every action, you have a gigantic and annoying reaction.
Leonard: Just when I thought you couldn't get any hotter.