The Big Bang Theory, Season 2

Penny:
I know this is none of my business, but I just... I have to ask - what's Sheldon's deal?

Leonard:
What do you mean, "deal"?

Penny:
You know, like, what's his deal? Is it girls...? Guys...? Sock puppets...?

Leonard:
Honestly, we've been operating under the assumption that he has no deal.

Penny:
Come on, everybody has a deal.

Howard:
Not Sheldon. Over the years we've formulated a number of theories about how he might reproduce. I'm an advocate of mitosis.

Penny:
I'm sorry?

Howard:
I believe one day Sheldon will eat an enormous amount of Thai food and split into two Sheldons.

Leonard:
On the other hand, I think Sheldon might be the larval form of his species and someday he'll spin a cocoon and emerge two months later with moth wings and an exoskeleton.

Penny:
Okay, well, thanks for the nightmares.