Leonard: Well, this time it's going to be different. Because I am like a romance ninja. You don't see it coming and then, bam, romance. Watch out! Hearts, kisses, love, ooh-ya!
Penny: You know, sometimes I think I've made you so much cooler than you used to be, and then you go and do something like that.

Sheldon: Woman, you are playing with forces beyond your ken.
Penny: Yeah, well your Ken can kiss my Barbie.

Raj: [to Amy] If you were having Sheldon's baby, would you really want him in the room?
Penny: Yeah, if he's in the room when they're making the baby, I'll give you $10.

Penny: I mean, who even reads Scientific American?
Leonard: It's kind of a big deal.
Penny: If it's such a big deal, how come the biggest celebrity they could get for the cover is a molecule?

Howard: She hid my XBOX like I'm a child. And my mom got me that for my birthday so if you don't give it back, I'm telling.

Bernadette: If you like pushing buttons so much, try pushing them on the washing machine.

Howard: A micro-valentine for a microbiologist.
Leonard: From her micro-husband.