At the title screen enter: A, B, X or Y (three times) then press R.
Change Wrestler attire
At the title screen enter: Hold X, L or R (speed code must be on)
Play as Keiji Mutoh
To play as the hidden boss character Keiji Mutoh, hover over The Great Muta at the character selection screen then hold the L, R and X buttons. If done correctly, the screen will flash for a brief second. Now press the A button on The Great Muta to play as Keiji Mutoh.
Sound Test
At the title screen enter: Up, Down, A, Up, Down, A.