Update: It was a fake
There are images of a Dr. Mario themed stage for Super Smash Bros that are currently making their way around the web. It is interesting that they have appeared today when we heard news of the massive Super Smash Bros update which is due to arrive on July 31st. The images originated from 4Chan, but they do look reasonably legitimate. Guess we shall have to wait and see.
Thanks, Takamaru64 and Steve