Fire and reload the lightgun or controller at a blank portion of the main menu to spell out the code words. The number of times Fire is pressed corresponds to a letter in the alphabet, with 1 being the equivalent of "A" through 26 being the equivalent of "Z". Press Reload to move on to the next letter.
Master code
Enter "MEBIGCHEAT" as a code. Press Fire(13), Reload, Fire(5), Reload, Fire(2), Reload, Fire(9), Reload, Fire(7), Reload, Fire(3), Reload, Fire(8), Reload, Fire(5), Reload, Fire, Reload, Fire(20), Reload at the main menu. If you entered the code correctly, the screen will flash.
Arcade mode
Enter "BLAM" as a code. Press Fire(2), Reload, Fire(12), Reload, Fire, Reload, Fire(13), Reload at the main menu. If you entered the code correctly, the screen will flash. The "Arcade Mode" option will now be unlocked in the extras menu. If you entered the code correctly, the screen will flash. Alternately, successfully complete the game.
Country challenges
Enter "ABROAD" as a code. Press Fire, Reload, Fire(2), Reload, Fire(18), Reload, Fire(15), Reload, Fire, Reload, Fire(4), Reload at the main menu. If you entered the code correctly, the screen will flash.
Mighty Joe Jupiter mini-games
Enter "MIGHTIER" as a code. Press Fire(13), Reload, Fire(9), Reload, Fire(7), Reload, Fire(8), Reload, Fire(20), Reload, Fire(9), Reload, Fire(5), Reload, Fire(18), Reload at the main menu. If you entered the code correctly, the screen will flash. Alternately, successfully complete all Mighty levels in cadet training mode to unlock the "Mighty Joe Jupiter Trilogy" option in Mighty Joe Jupiter mode. Complete the easy levels in cadet training mode to unlock Mighty Joe Jupiter Episode 2. Complete the normal levels in cadet training mode to unlock Mighty Joe Jupiter Episode 3.
Jukebox and music test
Enter "LETSBOOGIE" as a code. Press Fire(12), Reload, Fire(5), Reload, Fire(20), Reload, Fire(19), Reload, Fire(15), Reload, Fire(15), Reload, Fire(7), Reload, Fire(9), Reload at the main menu. If you entered the code correctly, the screen will flash. Alternately, successfully complete all episodes in the Mighty Joe Jupiter Trilogy to unlock the "Music Jukebox" option at the Options screen.
New Weapons
Finish the game using arcade mode with the weapon indicated to get the new weapon when starting a new arcade game
Finish the game 1 time to get arcade mode and Mirror mode
Get Hyper Arcade Mode
Finish the game 1 time in arcade mode using shotgun to get Hyper Arcade mode
Get Mighty Joe Jupiter Trilogy
Use cadet training mode and finish all Mighty levels. Complete those to get normal mode levels (Joe Jupiter Episode 2) and finish those to get Joe Jupiter Episode 3
