1853 Wild West level rewards
Successfully complete the level in story mode under the medium difficulty setting to unlock The Colonel as a playable character in arcade mode.

1920 Aztec Ruins level rewards
Successfully complete the level in story mode under the medium difficulty setting to unlock Stone Golem as a playable character in arcade mode.

1972 Atom Smasher level rewards
Successfully complete the level in story mode under the medium difficulty setting to unlock Khallos as a playable character in arcade mode.

2019 NeoTokyo level rewards
Successfully complete the level in story mode under the medium difficulty setting to unlock Sadako as a playable character in arcade mode.

2280 Return to Planet X level rewards
Successfully complete the level in story mode under the medium difficulty setting to unlock Ozor Mox as a playable character in arcade mode.

Arcade Adios Amigos level rewards
Successfully complete the level with a "Gold" rank to unlock Hector Babasco and Lean Molly as playable characters in arcade mode.

Challenge Pane In The Neck level rewards
Successfully complete the challenge with a "Silver" rank to unlock the Rotating Heads cheat.

Ending bonuses
Successfully complete the game under the easy difficulty setting to unlock the Cardboard Characters cheat and Streets level in arcade mode.