Bust-A-Move Millennium Cheats - GameBoy Color
Primary Collection of Cheats
Hidden levels
Press [B], [Left], [Right], [B] at the main menu.
Hidden mode
Press [Left], [Right], [B]x2 at the main menu. Select puzzle mode, then "Wide Field". Alternately, press [A]x2, [Down], [Up] at the main menu. Select puzzle mode, then "Normal Field".
Bonus characters
Press [B], [A], [B], [Down] at the main menu to unlock eight more characters.