If you would like to Master every stage, you will have to do the following: save all of the lives of the Innocents, find every one of the buried Treasure Chests (Secret Chests), collect every item in the stage (Koins, Diamonds, Armor... Everything, basically), and defeat every enemy in the stage (including those Evil Bunnies.) If an enemy falls off of the stage, it is counted as a kill. If you collect an item and die, you will have still collected the item. You will be rewarded with Art Galleries of concept images.