Back in the early 1980's, when Mario had only recently been officially named in the Donkey Kong Jr. arcade game, and had not yet become Nintendo's mainstay mascot, he moonlighted on a completely unlicensed basis in a game for Radio Shack's TRS-80 Color Computer.
Now, the CoCo was always a small market, which made it a haven for titles "inspired by" coin-op games with little concern for licensing. Mario had already appeared on the platform in a couple of unlicensed Donkey Kong games, including the great Donkey King, later rechristened The King.
And so it was that Tom Mix Software of Grand Rapids, MI conspired with a developer whose name escapes me to release Crash, a "new" Mario game. In this one, Mario started out flying a plane, which immediately crashed, sending him on a journey through four treacherous screens to safety. The game was not very well done -- the lazy graphics management was set up along byte boundaries, so sprites took huge 4-pixel jumps when moving horizontally, a serious limitation in a platformer. And it was fairly easy -- I beat it in a day or two, and it wasn't really entertaining enough to keep me coming back. From what I can recall, there were spiders to dodge and islands to jump across and ropes to cross -- it wasn't a very Mario-esque game, really, but it was an interesting effort in the absence of a Nintendo sequel to rip off properly.
Just an interesting footnote from the wild-and-wooly 8-bit gaming days. Although I privately like to think that it really WAS Mario, and Nintendo punished him for his after-hours shenanigans by replacing him with "Stanley the Bug Man" in Donkey Kong 3.