If you want to see a ??? type arceus there is one on Bulbapedia: http://bulbapedia.bulbagarden.net/wiki/???_(type) or you could hack it onto your game (not meant to take seriously) and marvel at it during battle. EDIT: I also found another bulbapedia page with the back sprite of the ??? type arceus: http://bulbapedia.bulbagarden.net/wiki/Pokémon_Diamond_and_Pearl_beta The arceus was first programmed into the beta of D/P.
