Mobius

Mobius is the homeworld of Sonic the Hedgehog and one of the main settings in Mario and Sonic Worlds In Danger. Dr. Eggman has tried countless times to take over Mobius and build his empire, the Eggman Empire. Each of these schemes are foiled by Sonic and his several friends and allies. However, now that Eggman has teamed up with Bowser, the two villains are trying to merge Mobius and the Mushroom World together in order to create the ultimate empire. The two planets are merging as we speak, which causes dimensional portals to open up through the worlds, allowing Mario to travel to Mobius, and Sonic to travel to the Mushroom World.