Super Mario Maker was a stage in Smash 4 and it returns to Ultimate. It’s based on Super Mario Maker on WiiU which was one I missed, but I did play its sequel Super Mario Maker 2 on the Nintendo Switch.
You can’t create any levels, but you can see a “computer” do it. While I’m sure there are only a certain batch of cycles, it all does seem rather random.
Even if the stage doesn’t change, the graphics will filter between all the 2D Mario versions. Just like the Super Mario Maker games.
While not quite my favorite stage, it’s a good one.