At the title screen, hold down right and simultaneously press B three times (pressing A also works), then hit start.
At the title screen do the following:
Hold down Right, pres B 3x then press Up, and release it. Press B 3 more times. Press Left, then release and press B 3 more times. Press Down, release, then press B 3 more times. Finally press Start
Successfully complete both of the quests and at the second screen of the ending, press A, B, Up, Down, A, B, Left, Right. If done right, you'll get the credits for the game.