He'd probably still be living with his mom!

All [Singing about Howard to Bernadette]

Leonard: Is that a pregnancy test?
Penny: Oh, yeah, just the first one. I didn't save them all.

And, not just on the cheek. On the mouth ... like mommies and daddies do.

Sheldon

Leonard: Buddy, I don't think you can. I mean, once it's out there, it's out there. This thing is like the science equivalent of a sex tape.
Sheldon: You know, frankly, I'd prefer a sex tape.
Leonard: You don't know what a sex tape is, do you?
Sheldon: No.

Amy: So you just got lucky?
Sheldon: Sheldon Cooper doesn't get lucky.
Amy: You and me both.

I feel like my mind just made a baby. And, it's beautiful. It's not like human babies which are loud and covered in goop.

Sheldon

Penny: Just you wait and see. I'm gonna romance your freakin' ass off.
Leonard: That's beautiful. Is that Shakespeare?

Sex doesn't count.

Penny

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.

The Big Bang Theory Season 7 Episode 6 Quotes

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.