The definition of updog is “a midget fucking a dead rabbit while on top of the Empire State Building and eating a bowl of carrots. At the end of the process, the midget is visited by John Stamos and then John punches the midget until he throws up the carrots, and then john eats the carrots and the process repeats.
Updog” is a made-up term based on a wordplay of the colloquial expression “what’s up, dog?” that is commonly used as a practical joke. Hey, Billy updog? to elicit the question what's updog? to which the prankster typically responds with the punchline "Nothing. What’s up with you? The original Ligma