That didn't take long.
Just four days ago, you could play the first level of Super Mario 64 in your browser with the Unity Web Player plugin. Made my Roystan Ross as a way to test his new Super Character Controller, which would allow people to have third person in Unity engine games, everything but the meshes for Mario, goombas and the Power Star had been remade. And even though Ross said there was no intent to monetize it, Nintendo made him take it down anyway.
If you downloaded it, however, you can keep playing like there's no tomorrow.
It's kind of a shame that companies are so protective of their IP, because things like this are pretty cool to see. It is what it is, however. Maybe we'll see another demo for the Super Character Controller in the near future.