The Legend of Zelda Collector's Edition Cheats

When you enter the Hyrule Castle courtyard, look at the right window. If you look inside the window, you will see paintings of Mario, Peach, Yoshi, Luigi, and Bowser.

When you meet up with the mask salesman, look at the giant backpack he is carrying. You will notice that one of the masks on it is a Mario mask.

If you look at the broach that Romani is wearing in Majora's Mask, you will notice that it is actually Bowser's face. When playing Ocarina of Time, Malon is wearing the same broach.