Sonic's planet

Sonic's planet, the main setting of the Sonic the Hedgehog series, has different characteristics and even different names across various continuities.

Earth
In the continuity of the Sonic video games, Sonic's planet is a fictional version of the planet Earth. The majority of its population are humans, but anthropomorphic animals like Sonic are common enough to not cause alarm among the populace.

The geography of the planet is similar to the real Earth, but it has its own lands and countries.

Parallel Earth
In the continuity of Sonic X, Sonic and his friends come from an unnamed planet that is in a parallel dimension to Earth (the main setting of the first two seasons of the series). A long time ago, Sonic's world and Earth were once one, but a cataclysmic event split the planet into two and sent them to different dimensions. The flow of time in Sonic's world is considerably slower than on Earth, with one month in Sonic's world equaling an entire year on Earth.

When Sonic came to Earth, the two worlds began to merge into one once again, which would ultimately stop the flow of time completely, thus forcing Sonic and co. to return to their world.

In this series, Earth is based on the setting established in the video game series, with a majority human population and political bodies based on those in the games. However, in Sonic X, anthropomorphic animals are completely unknown on Earth until the arrival of Sonic and friends. On the other hand, Sonic's world is completely populated by anthropomorphic animals, and the only native human is Doctor Eggman (who was himself originally from Earth but crossed over many years before the series).

Mobius
Mobius was originally established as Sonic's home planet in the Sonic Bible during the production of the original Sonic the Hedgehog game in 1991. Mobius was the preferred setting of the series in Western localisations until the release of Sonic Adventure in 1998, and continuities pre-dating this game continue to use Mobius as a setting.

Continuities in which Sonic's homeworld is identified as Mobius include:
 * Archie Comics (in which it is revealed that Mobius is a future/post-apocalyptic) version of Earth)
 * Sonic the Comic (in which Mobius and Earth are distinct planets in different dimensions)
 * Adventures of Sonic the Hedgehog
 * Sonic the Hedgehog (SatAM)
 * Sonic Underground
 * Other media based on the early Sonic canon, such as the Virgin Books series

Planet Freedom
Planet Freedom is the setting of Sonic the Hedgehog: The Movie. Its populace includes humans, anthropomorphic animals, and hybrids of the two. It is split into two parts: the Land of the Sky (home of Sonic and much of the planet's population), and the Land of Darkness (home of Doctor Eggman).