I believe that the Galaxys in SMG2 aren't natural Galaxys and are the result of Bowsers "Master Plan". For example, most Galaxys in World 1 could have been ripped from the planet itself. I also believe that each "World" is actually one of the planets in the Solar System, that were scattered throughout Time and Space(Thus, explaining the need for Portals). Notice that each World Map has one large Planet-like structure that all of the Galaxys orbit around! I believe that World 2's planet is a Fiery gas giant and that the Worlds Galaxys(mainly Boulder Bowl, Cosmic Cove, and Wild Glide) are the scattered remnants of the Planets habitable moon. All of the Galaxys could be easily explained this way, the only flaw is that there are Seven (known)Galaxys, but only 6 Worlds(Special World is arguably, Non-Canon). Also, the closer you get to "Bowser's Galaxy Generator" the more ravaged the Worlds are by Black Holes, and the more they start to look like Bowser's, Dream Empire(Pools of Lava, Castle, etc.)! I have been looking for a serious thread like this one for a LONG time, and I was beginning to think I'd never find someone who shares my interest in all things Mario.