The series takes place on Mobius, a planet mostly populated by anthropomorphic animals. A warlord and scientist named Dr. Robotnik takes over the city of Mobotropolis (renaming it Robotropolis) and uses a machine called the Roboticizer to turn most of the city's inhabitants into robotic slaves. A handful of citizens escape to Knothole, a village hidden within the Great Forest. Led by Sonic and Princess Sally, the citizens, now calling themselves the Freedom Fighters, battle to liberate Mobius. (Source: Wikipedia)