Unlock Cardboard Characters
Beat the game on Easy difficulty to unlock cardboard characters.

Unlock Characters in Arcade Mode
Earn a Gold medal in "Adios Amigos" (Arcade Mode) and unlock playable characters Hector Babasco and Lean Molly.

Unlock Characters in Story Mode
Beat the level and unlock these secret playable characters:
Medium level difficulty
2280 Return to Planet X: Ozor Mox
2019 NeoTokyo: Sadako
1853 Wild West: The Colonel
1972 Atom Smasher: Khallos
1920 Aztec Ruins: Stone Golem

Unlock Rotating Heads Cheat
Beat "Pane in the Neck" in Silver (Challenge Mode) to open up Rotating Heads cheat.

Unlock Streets Arcade Level
Beat the game on Easy to unlock the Streets arcade level.