What is updog?

It seems like you've set up a classic joke or prank called "updog." The idea is to get someone to ask, "What's updog?" to which you can respond with a play on words like "Not much, what's up with you?" It's a humorous setup that plays on the curiosity of the person being tricked.

If you're looking for serious information on an actual topic called "updog," please provide more context or specify what you're referring to, as "updog" in this sense doesn't have any known serious or significant meaning.