Butterfly 64 DS is a meme ROM hack of Super Mario 64 DS by Skelux, and is a port of their Butterfly 64 hack of the original Super Mario 64. Rather than a game, it is an exhibit of a butterfly flying in a circle. The only working controls are rotating the camera left and right on the touchscreen, and there is no other way to interact with the software.
The only known place to download it is this archived link.