Various cheats
     At the advanced option screen type in these codes:

Cheat code:             Effect:
2504                    Free Play On
1971                    Player 1 Invincible
1515                    Player 2 Invincible
4774                    Finish Game After First Round
3871                    Play As Grox
9021                    Play As Exor
9997                    Play On Secret Level
1037                    Easy Fatalities