Select the "Restore From Password" option from the "Game Setup" screen. Enter one of the following password to enable the corresponding cheat function.

Effect Password

All black opponent FQSTER
Bloody, headless opponent RUBE
Double game speed HYPER
Expert mode SUPERG
Invincible player one MAXX
Neon player two NUCLEAR
No time limit, three knockdowns wins 2LT
Power punches MRBUCKEYE
Short opponent WEASEL