During gameplay, press start and enter the following.

Level select:
Press Left, Up, , , Left, Up, , , Left, Up, , , Up,Up, Up, Up, Up.

Unlock every bonus game :
Press Left, Up, , , Left, Up, , , Left, Up, , , , , , , , . Quit your current game and go to the 'Bonus' menu.

1000 coins:
Press Left, Up, , , Left, Up, , , Left, Up, , , Up, Right, Down, Left, Up.

Full health:
Press Left, Up, , , Left, Up, , , Left, Up, , , Up, Right, Down, Left, Up.

Cage Drop mini-game:
Beat 59 missions.

Cloud Maze mini-game:
Beat 45 missions.

Floating Floor mini-game:
Beat 31 missions.

Movie Stills and Crash Coliseum mini-game:
Beat 70 missions.

Ring Coliseum mini-game:
Beat 21 missions.

Thanks to Revolution readers Wang Chun, Jim Connor, CoolErik, Rambojo and Clyde!