Play as Shadow:
Highlight the ? box and press Select 5 times. Now press any button.
Play as Marionnette:
Highlight the ? box and press Select 7 times. Now press any button.
Play as Image Talbain:
Highlight Gallon, hold Select, and press all three Punch or Kick buttons
Play as Oboro:
Highlight Bishamon, hold Select, and press any button.
GameShark Codes
Infinite Health P1801c0e540120 801c0e560120 Infinite Health P2801c12280120 801c122a0120
Thanks to Revolution readers Shin Akuma, Angel, Guilherme Henrique, and Scotty-G!