In-game reset - While playing the game, hold A + B + X + Y and press Start to return to the main menu.
Play as Carbuncle - Successfully complete the HaraHara course with either less than four or more than twelve fevers without any continues to unlock Carbuncle. Alternately, successfully complete the game with your number of continues as a multiple of 7.
Play as Popoi - Successfully complete the WakuWaku course on the normal difficulty setting to unlock Popoi.