Mario Galaxy is the Mario stage in Smash 4 (well, one of them). It's from Super Mario Galaxy, which means that this stage is IN SPACE! This stage takes place on a planet (specifically, the one from the Gateway Galaxy at the beginning of the first game). Like in Galaxy, the planet has its own gravity, but it's not very noticeable. Also, Starship Mario appears in the background. I don't really have much to say about this stage, really.