In this 3rd cartoon of Sonic the Hedgehog, Sonic and his two siblings, Manic and Sonia are the hit rock band, Sonic Underground. But in reality they are the children of Queen Aleana, the queen of Mobius. Queen Aleana was dispatched from Mobius by Sonic's enemy, Dr. Robotnik who turned Mobius into a waste land. So now Sonic, Manic and Sonia must fight Dr.