Alternate Background Menu:
Successfully complete the game.
Alternate costumes:
Successfully complete the game, then start another game in special mode. Only characters that survived will have an alternate costume.
Gallery 1:
Successfully complete the game under hard difficulty setting.
Gallery 2:
Successfully complete the game in the special mode.
Laser-sight pistol:
Successfully complete the game under the normal or higher difficulty setting, then start another game in special mode. The first available gun will now be a pistol with a laser sight.
Special mode:
Successfully complete the game.