Leonard: And this is a high-pulse laser with a BBO crystal. It's pretty cool. It emits photons in discrete bursts.
Beverly Hofstadter: Huh. Very impressive.
Leonard: But?
Beverly Hofstadter: But what, dear?
Leonard: Oh, I don't know. It's just, usually there's a "but" followed by something that makes me feel bad.

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: I'm looking over my text correspondence with Beverly and I don't see anything that would have given her offense. Nothing's ambiguous, I spell everything out. Including "laugh out loud" and "what's the fracas?"

Amy: Are you really not gonna pick up your mother?
Leonard: No. It's fine, she likes to take a cab or a shuttle. That way she can meet people.
Amy: Well, that's kind of nice.
Leonard: Yeah, she always says that a stranger is just a person whose emotional weak point you haven't found yet.
Sheldon: Your mom is the best.

Leonard: How was your flight?
Beverly Hofstadter: There were some parents with a baby. A lot of crying.
Leonard: Well, babies do that.
Beverly Hofstadter: No, it was the parents. It seems they couldn't handle some constructive criticism.