Cheat mode - At the main menu, highlight "Versus" mode, then hold L + B + R (in that order), then release B, R, L (in that order) to display the cheat entry screen. Enter one of the following codes to activate the corresponding cheat function:
Gallery photos - Play through the game on hard difficulty setting. While fighting, various buildings that you destroy will have special Atari power-ups inside. Collect these to unlock a gallery picture.
Mothership level - Successfully complete adventure mode with Mecha Godzilla to unlock the Mothership level.
Special moves - Moves that are special to some monsters can be executed by pressing R + L or A + Y. For example, Gigan teleports and Megalon digs underground. Note: While underground with Megalon you have to continue holding these buttons to move around. Target yourself under your opponent and execute a grab. You will emerge from the ground with the opponent in your hands. If you miss, you will be standing open to attack because you are exhausted from digging.
Taunt - To do a taunt, press B + X or A + X.