An alternate ending can be seen if every stage of is finished within 5 seconds or less remaining on the clock. This also applies to Haguruman 2.
Enter these codes at various points to unlock their effects.
A set of special stages can be accessed by playing on hard mode and activating the warp gate in stage 64. Activating the gate will take you from stage 64 to stage EE which continues through all of these stages: EF, F0, F1, F2, F3, F4, F5, F6, F7, F8, F9, FA, FB, FC, FD, FE, FF, and finally 00 which upon completion will loop you back to stage 1 again.
This trick will let you see the credits of Guadia Quest without having to go through the entire game, thus earning you the medal that recognizes your completion of the game (for Arino's final challenge). First go to the Mausoleum (the path to get to the Mausoleum is located east of Centraan between some mountains and the ocean; you will need to enter the path from north of the mountains). After you go into the Mausoleum, walk nine steps up (you will be in the top left corner). Then press "A" to open the menu and select "Look." You will discover hidden stairs. Talk to the man below and answer all his questions with "yes" and he will show you the credits of Guadia Quest.
Enter these codes at various points to unlock their effects.