In story mode, enter the following as your user name.
DEATHGAMER - All Wrestlers and Arenas
tpiperi - Big Feet Mode
okendall - Big Hands Mode
rtaylor - Big Head Mode
tho - Big Head, Big Hands, and Big Feet mode
mbilodeau - Cartoon backgrounds
pstapley - Cartoon character
edma - First Person Camera mode
pjefferies - Ghost mode
ksimeonov - Greyscale mode
jgintu - Halo mode
stomanovski - Hardcore Al
denicholas - Invulnerable Players
jche - Player 1 Invulnerable
ddaniels - Player 1 unlimited supers
cbarlow - Player 2 Invulnerable
jmaxwell - Player 2 unlimited supers
donttrythisathome - Unlock all cheats
ewilliams - Wireframe mode

Song Selection
This code is entered while a match is taking place in any arena - Push L1 and L2 at the same time. Hit the same buttons again to cycle through the different songs.

Unlock Everything (enter the following code at the main menu screen)
Hold down L1 and press X, square, triangle, O, X, square, triangle, O.

Unlocks new Cheats menu at the options screen
At the main title screen, hold L1 and enter the following:
X, Triangle, X, Triangle, Circle