Leonard: I'm gonna see where he is.
Penny: How?
Leonard: I know his password so I can track his phone.
Penny: You do that?
Leonard: Not always. But ever since he wandered off at the swap meet chasing a balloon, I get worried.

Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

Leonard: Penny, as a scientist, my job is to figure out why things happen. But I don't think I'll ever understand how someone like me could get to be with someone like you. You know maybe I don't need to understand it, I just need to be grateful. I love you, Penny.

Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?

Penny: [on the phone] No, mom. It's the same guy I've been going out with for the past two years. Yeah, the scientist. Well, it's complicated. He works with lasers and atomic magnets. No, I did not see it coming. No, we have not set a date. No, I am not pregnant. Yeah, this is a first for our family.

Howard: Hang on, I know a place where you could you stay and earn some money at the same time.
Stuart: Great!
Howard: I just have to warn you: it will involve humiliation, degradation and verbal abuse.
Stuart: So, what's the catch?

Bernadette: But we have jobs, we can't babysit her twenty-four hours a day.
Howard: What if we use our vacation time?
Bernadette: I wanted to go to Hawaii, not Hell.