At the main menu, hold L1 and press X, Square, Triangle, Circle, X, Square, Triangle, Circle to unlock all cheats in the game.
From there you can use one of the following name codes:
Unlock the following extras, do the tasks listed below:
Knock out your opponent and catch the mattress on fire. After that, your opponent will probably wake up. Knock him out again, then grapple him and walk him over to the fire. Let him get out of the hold, then you can walk out of the fire. If he is able to get out of the fire, repeat.
If you get tired of the music playing while you are wrestling, press L1 + L2 to change it.