Sheldon: Wonderful. Although I'm not sure how I feel about being used as a guinea pig.
Leonard: Well, when you get the machine, you can find out.

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: He really worked with the Drug Enforcement Agency?
Penny: He didn't know it 'til he was cuffed, but yeah.

Amy: Well, everybody has things that they need help with. Like me. I can't see without my glasses. And right now you're just a cute, pink smudge wearing a childish green smudge.

Bernadette: You know, I just read that a team at MIT developed a device that helps people read human emotions.
Leonard: And you think we can get those guys to reprogram Sheldon? Cool.