Successfully complete the game on the Normal difficulty setting to unlock the Hard difficulty setting. You may also start a new game to access a bonus sub-quest and have all previously unlocked costumes, money, and the drill power-up available. Although you will have to find the Headgear again, they will be at their previous levels.

Successfully complete game on the Beginner, Normal, Hard, and Happy difficulty settings. Start new game and get the drill then return to town. You can find Popon in front of Fan's cake shop. Talk to her and you will be able to play as her.

Successfully complete game on the Beginner, Normal, Hard, and Happy difficulty settings. Start a new game and go to the final locked house in human town and enter "LEGENDARY" as a password to unlock Boss Rush mode. Note: Enter "yarushikanaiwane" as a password in the Japanese version in Hiragana/Katakana. Boss Rush mode allows all eight Bosses to be fought in succession.