Advantage
When you enter a room with a creature in it, run around until you can get behind it and then attack. If you did it right the game will say "advantage" on the top of the screen and you will come into battle fully charged. You will also be able to hit the creature in the back(it does more damage when you hit a creature in the back).
submitted by sephiroth

Open cheat mode
Beat the game. At each saving point save, and restart the system. Change the resolution after each time you do this. (note: you must start with resolution set on "high res. letterbox" then cycle up from there.)This will add a cheat menu at the title screen. There is:

Invincibility - on/off

All moves - on/off

All items - on/off

No key renewing - on/off

Play as any monster - select

Play as Alien - on/off

Play as Pres. - on/off

Level select - 0-0

submitted by Clown

Play as Alien
To play as the alien who wears the red dress- enter the following combination of button presses at the title screen: L button, R Button, L button, R button, and Z.

Note: this code only works after you beat the game on Ultimate difficulty.
submitted by N64 Man

Play as President Weller
To play as president Weller- enter the following combination of button presses at the title screen: L button, R Button, L button, R button, and start.

Note: this code only works after you beat the game on Ultimate difficulty.
submitted by N64 Man