Pause game play and press Up(2), Down(2), A, Up(2), Down(2), B, Up(2), Down(2),C.
Hidden Endings
To view the hidden endings, go underground in the Junkyard stage. Climb the wall with mounted guns, instead of blowing it up to descend further. Once atop the wall, find a man who will allow you to fight three bosses in consecutive tournament matches. Defeat the opponents to view the hidden endings.
Infinite lives
To get unlimited lives, just before you start the game press Up, Up, Down, Down, Left, Right, Left, Right, A, B, B, A. This code need to be entered quickly and will take some practice.
Secret Level
In Stage 3,the garbage dump, right before you fight Noiman,in the room with 3 turrets, jump up and climb the wall. A guy will ask you if you want to enter the battle arena.