Go to the "Press Start" screen and enter CIRCLE, RIGHT, UP, RIGHT, DOWN. A sound will confirm this.
Unlock Big Ape Arena
Enter CIRCLE, R2, R1, CIRCLE, R2, R1 at the "Press Start" screen. The mat will now look like the game's creators.
Unlock Big Head Mode
Go to the "Press Start" screen and enter the following: CIRCLE, L1, L1, L1, UP, DOWN. A sound will confirm correct code entry.
Unlock Bonus Match Up
At the "Press Start" screen press CIRCLE, UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT. "Bonus Match Up" should now appear at the top of the screen. This mode will now be available to select. This mode lets you sweet new arenas with the tougher wrestlers in the game. Drooling aliens, Kang and Kodos, and Itchy and Scratchy to name a few.
Unlock New Credits
Enter CIRCLE, L1, CIRCLE, L1, CIRCLE, R1, CIRCLE, R1 at the title screen to unlock the cooler credits.