There is an unused Skull stage that can only be accessed by using Gameshark code 800FE55B 000A. At first the stage will appear black, but pausing and selecting "Restart this Match" will get it to appear properly.

Stage is largely a flat, circular arena with a unique texture painted on the ground. The skybox consists of an image of a skull stretched over the arena, with flames lit behind it. The stage also has some trouble loading the proper music from round to round.