World 4 (Super Mario Bros. 2)

World 4 is the fourth of the seven worlds in the game Super Mario Bros. 2, which is actually a graphical hack of the Japanese Doki Doki Panic. The world has a unique snow and ice theme to it, and introduces the player to the Flurry and Autobomb enemies. The final boss is Fryguy, who is an intentionally out-of-place for this world, being a fire creature in an ice-covered world. Level 4-1 is notable for being the only level in the entire game without a boss, instead having at the end a room filled with a huge amount of enemies, with the boss music playing in the background and the crystal ball lying unguarded on the ground at the end. Also, Birdo is strangely seen as a seemingly normal enemy early in level 4-3, and reappears after being defeated whenever the player reenters the room it is in, allowing it to be defeated an infinite number of times for massive points. The actual purpose of this out-of-place Birdo is for the player to ride on one of her eggs across the otherwise impassable ocean to reach the main dungeon.