Leonard: Hey, Zack. Um, look, I-I know this is gonna be disappointing, but, um, I-I can't do this. No, no, no, no. I-I, I know how. I just can't. (stammers) But, hey, look, i-if you like, I-I know someone who might be interested.
[cut to Sheldon on the phone in Apartment 4B]
Amy: No! Absolutely not!
Sheldon: I'm sorry, my wife says I'm not allowed.

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.

Marissa: It's a little weird for us, too. I mean, instead of our baby looking like Zack, it's gonna look like Leonard.
Zack: Or Penny if it's a girl.
Penny: No, no, it's not gonna look- Sure.

Raj: Uh, if you still want to go, you can go to India and help my dad eat all the nonrefundable sushi.
Howard: Indian sushi? I need a change of underwear just thinking about that.

Zack: Well, Leonard, we were hoping you'd go in on Monday.
Leonard: Okay.
Marissa: And they say, for the best results, between now and then, you shouldn't have sex.
Zack: Sorry, bro, I know it seems impossible to go for five days without, but I believe in you.
Leonard: Five days? My record is 24 years.
Penny: Uh, I think that also means no flying solo.
Leonard: Oh. Then my record is 14 years.