a few years earlier wanted to do a Mario Bros. port for PC, after John Carmack had figured out how to fluidly scroll horizontally on a PC. But Nintendo wouldn't give them the license, and so they ended up making the Commander Keen games instead (which are available, but I don't know how similar they are).
When I was a kid I played I played a game on my Commodore 64 that was called "The Great Giana Sisters" (notice the parallel . It was made by a German developer, but had to be pulled off the shelves after legal threats from Nintendo. The game spread like wildfire though amongst C64 users, because (a) it was a great game, (b) it had some of the best music ever made on the C64 and obviously (c) because there was no official Mario port for the Commodore 64.
For all you 8-bit music aficionados, here's the Intro, which was a separate program that you had to load containing just the title screen and the music. I remember I used to load it just to listen to the music, even without going on to play the game.
Here's someone playing through the game: