Sometimes I forget how smart you are.

Penny: Is that why they're called Fig Newtons?
Sheldon: No. Fig Newtons are named after a small town in Massachusetts. No, don't write that down!

Leonard: How did you know my birthday's Saturday?
Penny: I did your horoscope, remember? I was going to do everybody's until Sheldon went on one of his typical psychotic rants.
Sheldon: For the record, that psychotic rant was a concise summation of the research of Bertram Forer, who, in 1948, proved conclusively through meticulously designed experiments that astrology is nothing but pseudoscientific hokum.
Penny: Blah, blah, a typical Taurus

Penny: Damn. You have more make-up than I do. You've got better make-up than I do. Yep, I'm borrowing ing this.
Leonard: Hey, hey, hey. This is my comic con make-up. I love you, but there are some things a man doesn't share with his girlfriend.

Leonard: We think we can help you with your stage fright.
Sheldon: Oh, I doubt that. I haven't figured out a way, and I'm much smarter than all of you.
Penny: Yes, buy you're not smaller than all of us put together.
Sheldon: I'm sorry, that is what I meant.

Leonard: Two can play this game.
Penny: Get up.

Penny: Maybe we should talk first.
Leonard: Okay, but before you say anything, have you ever heard of Schrödinger's cat?
Penny: Actually, I've heard far too much about Schrödinger's cat.
Leonard: Good.
[Leonard kisses Penny]
Penny: Alright, the cat's alive. Let's go to dinner

Penny [to Leonard]: Look, you are a great guy, and it is the things you love that make you who you are.
Wolowitz: I guess that makes me large breasts

Oh, they don't always get to ride the roller coaster. Sometimes they only get to spin the teacups.

Howard: I got pretty exciting NASA news today. Next week I fly to Houston for orientation and zero-gravity elimination drills.
Penny: What does that mean?
Bernadette: He's gonna to learn to poop in space.
Howard: Open the pod bay doors, HAL.
Raj: Maybe your nickname should be "Brown Dynamite."

Penny: God, he's an ass when he drinks.
Wolowitz: He's an ass he doesn't. You just don't hear it.

Penny: What actor holds the record for being named People magazine's Sexiest Man Alive?
Sheldon: William Shatner!
Leonard: I don't think it's Shatner.
Sheldon: Then it's got to be Patrick Stewart

TBBT Quotes

Oh, Bernadette, please play my clarinet.

Raj's poem

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?