Kaizo Mario World
Kaizo Mario World (also known as Super Mario World: Kaizo Edition, Kaizo, Asshole Mario, or any other form of the name) is a very difficult Japanese ROM hack of Super Mario World. The hack, well known for being one of the first very difficult SMW ROM hacks, quickly spread throughout the internet.
Kaizo Mario World was first created by T. Takemoto in 2007 for his friend, R. Kiba, to play through (his playthrough can be found here or here). The original name of the hack is
自作の改造マリオ（スーパーマリオワールド）を友人にプレイさせる, literally “Making my friend play through my own Mario (Super Mario World) hack”. Since part of the name, 改造マリオ, is pronounced as "Kaizo Mario", however, the name soon began to be shortened to that. With this, the term "Kaizo hack", used to denote a very hard ROM hack, originated as well.
The hack itself contains a large number of things that SMW Central would not accept in their hacks, such as floating and stacked munchers, overly difficult level design, unfair invisible coinblock placement, low time limits, and several other things. However, SMWC does in fact have a Kaizo hacking forum for those that do enjoy playing and making Kaizo hacks.