Several years ago, Nintendo released a Satalite System in Japan called "SatellaView". It allowed owners with a Super Famicom (Super NES in America and Europe) to access Nintendo news rooms, multiplayer games and of course Games to download.
Nintendo started to convert the original Legend of Zelda game to the Super famicom and each week allowed gamers to download a small part of the game (Like a dungeon) and run it on the Super Famicom. It was called "Zelda BS" meaning "Bandai Satellaview Zelda" . The graphics were SNES quality and looked a lot better than the NES game. However Nintendo started to change the game a bit so that it was a bit different from the orginal. The first dungeon for example was completly re-designed into an "S" shape and the item you collected was a Boomerang instead of a bow & arrow.
There is a dump of the game floating around the Internet at the moment, but unfourtunatly it seems to be a partial version. This being that the person who dumped the ROM did so after only the 3rd part and it's unknown whether a 4th part version (complete version) exists on the net.
Infact, many of locations of the game are like Zelda 64. Take this for example:
The second dungeon was Dodongo's Cavern. To get into it, you have to throw a bomb infront of the entrance. To kill the King dodongo you have to throw bombs in it's mouth. Sound familar?
Anyway, Nintendo did never finish converting the whole game - it was rumored they were working on a new SNES game which was taking up to much time - and to the fact the Sataview wasn't getting enough people accessing it.
It was also rumored after Mario All Stars was released, that Nintendo were working on a Zelda All Stars which included the first two Zelda games revamped with new graphics and Zelda 3 from the SNES. It never was made though.
Thanks goto Scott Jones for clearing up a few bits of info.