Mary Cooper: You know, you two make a cute couple.
Leonard: No, no we're not, we're not a couple, we're single, two singles, like those individually wrapped slices of cheese that are friends.
Mary Cooper: Did I pluck a nerve there?
Howard: Oh yeah.

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: [to a "smiling" Sheldon] We're here to see Koothrappali, not kill Batman.

Mary: He gets his temper from his daddy.
Leonard: Ah.
Mary: He's got my eyes.
Leonard: I see.
Mary: All that science stuff, that comes from Jesus.

Mary Cooper: I'm sorry, did I start that sentence with the words, "If it pleases your highness?"

Sheldon: I read an article about Japanese scientists who inserted DNA from luminous jelly fish into other animals; and I thought "Hey! Fish night-lights".
Leonard: Fish night-lights.
Sheldon: It's a billion dollar idea, ssh!