Play as Mecha Godzilla 2
Successfully complete adventure mode with all monsters, then complete adventure mode again with Mecha King Ghidrah.

Play as Mecha Godzilla 3
Successfully complete adventure mode as Orga on the hard difficulty setting.

Vortaak level
Successfully complete adventure mode with Mecha Godzilla 3 on the medium difficulty setting.

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.

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: