Kaizo Mario World

Kaizo Mario World, also known as Asshole Mario, is a series of three ROM hacks of Super Mario World, created by T. Takemoto. The term "Kaizo Mario World" is a shortened form of Jisaku no Kaizō Mario o Yūjin ni Play Saseru, with the word "kaizō" (改造) referring to ROM hacking. The series was created by Takemoto for his friend R. Kiba.

Kaizo Mario World features extremely difficult level designs using the SNES platforming classic's engine. The series is notable for deliberately breaking all standard rules of "accepted" level design and introduced many staples of later Kaizo hacks, such as placing hidden blocks where the player is likely to jump, extremely fast autoscrollers, dying after the goal post, and various other traps. These cruelties and the resulting frustration, as well as the skill level required, are both the purpose of the hacks and the appeal of any Let's Play videos made of them.