Terrible Grammar Puns

NOTE: My friend, the same one from this post, has a sister who's only 6. She has not yet learned the ways of the world, and the fact that it contains me and my terrible jokes.

I stumble into the living room, clutching my stomach and groaning.

Friend: What's wrong with you?

Me: I don't know, but I think I have a serious case of updog.

Friend's Sister: What's updog?

I stand up straight, with a big smile on my face.

Me: Not much, how about you?

Friend: Oh, Christ.

EDIT: Formatting and grammar.