Go to the Single or Endless mode starting menu, then press Up, Down, Triangle, Square, Start to unlock all characters.
Go to the "Gallery" selection at the options menu. Highlight the "View Cutscenes" option, then hold Square and press Up, Down, Left, Right to unlock all characters and intermission sequences.
To play as Popoi, complete the WakuWaku course on the normal difficulty setting.
To play as Carbuncle, get less than four or more than twelve fevers without any continues in HaraHara mode.