Leonard: Why does he need a baby? He's already hairless and smells like talcum powder.

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.

Bernadette: Still, I can't believe you can turn ordinary skin cells into functioning brain cells.
Amy: Well, I turned this one into a functioning boyfriend, so sky's the limit.

Raj: Well, I can't eat like a ten-year-old all the time.
Penny: You're dating somebody! Who is it?
Raj: What? What are you talking about?
Penny: You only watch what you eat when you're afraid you might have to take your shirt off.

Raj: Maybe there are other things we have in common. Come dinner-time, do you enjoy eating food?