Sheldon: There are post-prom mating rituals?
Penny: Not always. Unless your date drives a van with an air mattress, then always.

Sheldon: I may be an alien, but I have urges. If Amy wants to copulate by firing her eggs into space, well then I will happily catch them with the reproductive sack on my upper flermin. I'm not the best at reading facial cues, but I can see that you're a little turned on.

Leonard: I thought you were gonna pretend to be an alien.
Sheldon: I was, but Penny didn't want to. You didn't want to. Bernadette, Amy, Koothrappali and Wolowitz didn't want to. And even I knew it was weird to hire somebody.

Leonard: Was that a flask?
Sheldon: Yes. I've decided to embrace all the traditions associated with prom, including spiking the punch.
Leonard: You're gonna put alcohol in the punch?
Sheldon: Oh, no, this is pomegranate juice. It's all the fun of high-school hijinks, with the self-protecting zip of anti-oxidants.

Penny: Well you wouldn't have asked me either.
Leonard: I would have asked you. In my head. On the way home. While I was having a good cry.

Amy: You're making me worry. What's going on?
Sheldon: What's going is we're about to go to a prom and there's a great deal of pressure on young couples like us to engage in what Mr. Bob Eubanks called "makin' whoopee".

Stuart: So I met Jeanie at your Aunt Gladys's. She passed me the Manischewitz, I took one look at this punim, and almost plotzed on the kugel.

Raj: This is so messed up.
Emily: I know. I'm having the best time!

Stuart: Oh, so she's good enough for Howard but not for me?
Howard: Yeah.
Bernadette: Yeah. Go have weird relationships with your own mother and cousin. This is his turf.

Bernadette: Howard, get off of him.
Howard: Not until he stops humping his way up my family tree.

Sheldon: I really did think you looked pretty.
Amy: You did?
Sheldon: Yes. So much so that I started to panic.
Amy: Well you can relax. Just because you think I look pretty doesn't mean we have to spend the night together.
Sheldon: Were you hoping we would because it's prom?
Amy: I'm always hoping. But tonight, I just wanted to have a nice time with you. Maybe dance with someone who has arms.

Sheldon: Thank you for understanding.
Amy: Of course I understand. Sheldon, there's something else I've been wanting to say, but before I do, I just. I want you to know you don't have to say it back. I know you're not ready and I don't want you to say it just because social convention dictates -
Sheldon: I love you, too.
Amy: You said it.

Sheldon: There's no denying that I have feelings for you that can't be explained in any other way. I briefly considered that I had a brain parasite, but that seems even more far-fetched. The only conclusion was love.

Sheldon: Wow, wow, wow, wow. Just because I love you, doesn't mean girls are allowed in my room.

Raj: Okay, here we go. [to Leonard & Penny] Say cheese. [to Sheldon & Amy] Say cheese. [to Howard & Bernadette] Say cousin.