You're referring to the infamous Mugen Null Edits!
If you're interested in exploring more, you can still find archives of Null Edits and related content online, but be warned: some of these edits can be quite...unpredictable! mugen null edits
For those who may not know, Mugen is a popular freeware fighting game engine created by Elecbyte. It's known for its flexibility and customizability, allowing users to create their own games, characters, and content. However, this openness also led to the creation of... interesting... content. You're referring to the infamous Mugen Null Edits
The Null Edits, in particular, refer to a series of edited versions of the Mugen engine that were altered to allow for extreme, often broken, and humorous gameplay mechanics. These edits were typically created by a user named "Null" (or "Null edits") and shared online. It's known for its flexibility and customizability, allowing