No Gems:
Before the match begins in VS mode, both players must press and hold both the L & R buttons (Saturn) or Select (PSX). No gems will be given out during the match.

Pumpkins:
You must have the reality gem. Call on the reality gem, then when you have called upon it press the L+R triggers (Saturn) or Select (PSX) . You'll toss a pumpkin!

For the following codes to work you must have beaten the game at least once.

Play as Doom:
Start the game without shortcuts, then press Down, Down and hold Down, then press and hold Fierce Kick. Then press and hold Medium Kick, then press and hold Weak Kick, so that eventually you are holding all three buttons. If you do it quickly enough you will see Dooms face in the corner.

Play as Thanos :
Start the game without shortcuts, then press Up, Up and hold Up, then press and hold Weak Punch. While holding Weak Punch, press and hold Medium Punch, then press and hold Fierce Punch, so that eventually you are holding all three buttons It's just like the Dr. Doom code - everything must be done the same way.

Thanks to Revolution readers ShadowHawk, Michael Hinrichs and Chris Sexton!