A quick Google search yielded this:
http://cheats.ign.com/objects/142... Seems pretty interesting. Why the URL says "cheats" at the beginning, I will never know.
Basically, he's referring to the Super Mario World 2 game that Nintendo was going to make 3D by utilizing the Super FX chip, but decided otherwise due to the development of the N64. I didn't find any information on an uncovered prototype, though. Then again, I didn't look very long or hard.