Leonard: I have something that might help. It's-it's a recording of the only person whose opinion Sheldon actually respects.
Amy: Hawking? Feynman?
Leonard: No, himself.

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: Thanks, Dad. We're gonna give them hell.

Leonard: It's a pep talk he made when he was a kid. He gave it to me years ago and told me to save it for a real emergency.
Penny: What? You didn't break it out when he declared his room a sovereign nation and waged a trade war against us?
Leonard: His major export is talking. I didn't want that anyway.

Amy: Hey.
Sheldon: Hello.
Amy: "Fine with flags"?
Sheldon: Yes, flags, up there flapping around on poles. If you think about it, they're just the strippers of the emblem world.