Kaizo Mario World, also known as Asshole Mario, is a series of three ROM hacks of the 1990 Super Nintendo Entertainment System (SNES) video game Super Mario World, created by T. Takemoto. Kaizo Mario World completely reworks the Super Mario World level designs to make them extremely difficult. The hack deliberately breaks all normal rules of "good practice" level design, for example by placing invisible blocks where the player is likely to jump. This cruelty and the resulting frustration, as well as the skill level required, is part of the appeal of Kaizo Mario World Let's Play videos. Let's Play videos of Kaizo Mario World have received millions of views online.
The original title of Kaizo Mario World was "Making my friend play through my Mario hack (Super Mario World)", as it was created by Takemoto for his friend R. Kiba. All in all, Takemoto has created three Kaizo Mario World games: Kaizo Mario World 1
, Kaizo Mario World 2
, and Kaizo Mario World 3
The Japanese word Kaizou translates into English as "reorganize", "restructure", "reconstruct", or "hack". Kaizo Mario World's prominence means that the "Kaizo" name has been reused by other games not made by Takemoto as a way to indicate a sadistic level of difficulty, for example Kaizo Mario 64 (a ROM hack of Super Mario 64), and the Kaizo Caverns Minecraft map in Vechs' Super hostile map series. Some believe that the Kaizo ROM hacks gameplay style has inspired Nintendo's official Impossible Pack downloadable content for New Super Mario Bros. 2.