M.U.G.E.N. is a free, highly customizable 2D fighting game engine originally created by Elecbyte. Its name is a nod to the Japanese word for "limitless" or "infinite."
Released in 1999, M.U.G.E.N. is essentially a blank canvas. Instead of coming with a set roster, the engine allows players and creators to download, install, and customize almost everything, including

• Characters: You can add an infinite number of fighters. While many are ripped from classic titles like Street Fighter and Mortal Kombat, the community has also created thousands of original characters, ranging from anime stars to pop culture icons like Ronald McDonald.
  • Stages: You can fight anywhere, from classic King of Fighters backgrounds to entirely surreal custom environments.​
  • Screen Packs: These change the entire UI, theme, life bars, and menu layouts to match your game's aesthetic.​

Because of its open nature, M.U.G.E.N. is famous for allowing wildly creative, impossible crossover battles.
For a look at the chaotic and customizable battles you can create in the engine