Sex doesn't count.

Penny: Hey, how come you've never done anything romantic to celebrate our first date?
Leonard: Well, for starters, you've broken up with me so many times, which first date are we talking about?

Penny [to Sheldon]: Your food's ready.
Leonard: No, no, what are you doing? He's both happy and quiet. It's like seeing a unicorn and Bigfoot at the same time.

I'm not going to the mall with someone dressed like a dumb space bear.

That's right. My phone is just as smart as you guys.

Bernadette told me everything. Now you don't get the left or the right.

Leonard: They weren't boobies. They were muscles. And, the make-up was green, I was pretending to be the Hulk.
Penny: You were wearing her bra.
Leonard: That was to keep my muscles from sagging!

Penny: Not even the chapter on the breast feeding crisis?
Leonard: It was not a crisis. Apparently, I favored the left one, she got a little lopsided.
Penny: Oh, my God, you still go left!

Penny: Oh, come on. Why? How bad could it be?
Leonard: There-there's chapters about potty training, bed wetting and masturbation. Basically, if something came out of me, she wrote about it!

The Disappointing Child by Beverly Hofstadter.

Raj: I didn't want anyone to feel bad at the end of the game. Some of those puzzles were really hard. I didn't know who was going to get Penny.
Penny: Run.
Raj: That came out wrong. But you have to admit you had a wonderful time.
Penny: Run to India.

Sheldon: To the planetarium!
Penny: Let's go!
Leonard: To the Tar Pits!
Bernadette: Let's go!
Amy: There's a Neil Diamond concert next month.
Howard: Let's go!

TBBT Quotes

Sheldon: I recently read that during World War Two, Joseph Stalin had a research program to create supersoldiers by having women impregnated by gorillas.
Howard: What a sick use of science.
Raj: Hey, as long as the baby's healthy.
Amy: I wonder if Stalin considered any other animals.
Leonard: Hippos are the deadliest creature. A half-human, half-hippo soldier would be pretty badass.
Howard: Yes, but when they're hungry-hungry, you can stop them with marbles.
Sheldon: Yeah, the correct animal for interspecies supersolider is koala. You would wind up with an army so cute it couldn't be attacked.

Raj: Well, to paraphrase Shakespeare: It's better to have loved and lost than to stay home every night and download increasingly shameful pornography.
Penny: Oh... you poor baby.
Raj: What's wrong with me, Penny?
Penny: Nothing, nothing. You know, if we weren't friends - and you hadn't brought up that creepy pornography story - I'd be on you like the speed of light squared on matter to make energy.
Raj: Hey, you totally got that right. E = MC squared.
Penny: I listen. I have no idea what it means, but I listen.