Mobius is the home planet of Sonic the Hedgehog, Shadow the Hedgehog, Dr. Eggman, etc. In Super Smash Bros. Crossover, it was mentioned several times. Infinity Mecha Sonic killed every inhabitant prior to Super Smash Bros. Crossover, and turned Mobius into a barren wasteland. Mobius makes its first appearance in Season 17, when Sonic and Shadow are teleported there for the final showdown with Mecha Sonic. Mobius is restored to its original state after the Heroes of Legend recreate the Smash Bros. Galaxy, which it has become a part of along with Earth-2149.
In Season 40, The Galactic Empire turned Mobius into a Capital Planet and destroyed Sonic the Hedgehog, Shadow the Hedgehog and friends and enslaved it's inhabitants. Mobius was then transformed into a advanced technological planet.