There's not much to do inside the level, mind you, but it's an interesting proof of concept for sure.
Of course, you can't just grab a world from Minecraft and put it in a DS game willy-nilly. The level itself had to be modeled from scratch, then imported using specialized modding tools developed especially for the game.
Why would anyone do that, you might ask. Well, why the hell not?
Minecraft in SM64DS [YouTube]
Questions? Comments? Contact the author of this post at andras-AT-kotaku-DOT-com.