At some anime cons that I go to, they have this event called Random Battle Group which is shortened to RBG. Basically there are two teams and you fight like an active time battle. Everone takes their turn to attack the other side. They just for fun and sometimes really random stuff happends during them. Here is an interesting one from Ohayocon 06.

http://youtube.com/watch?v=on9cwE92ZKQ