Milon's Secret Castle/Secrets and codes

Continue your game (Famicom / NES)
In order to continue your game, you must obtain the first crystal from the boss on the first floor. Once you possess this crystal, you can continue your game after you lose all of your health by returning to the title screen, holding and pressing.

Extra Ending Message (Famicom / NES)
Beat the game twice in a row to get an extra ending message.