Published on September 4, 2008 super-easy to get. just go to arcade mode (in Cantina) and play against a friend locally (or use another controller and play with yourself...nevermind).
just make player 2 jump off the edge in the first level 100 times and there you go. it shouldn't take any longer than 5 minutes.
Tip: walk slowly towards the edge and when you jump off you'll respawn right back where you stood before so it will make it go by faster.