Sonic-Zilla is an alternate version of Sonic the Hedgehog from an alternate version of Mobius. In this universe, Chaos Emerald radiation transformed Sonic into a hideous, gigantic monster that threatened the people of Mayor Kintobor's city. Somehow half a Chaos Emerald became embedded in his chest like his father, Jules-Zilla. After an anguished Sonic the Hedgehog in Giant Robotno accidently killed Jules-Zilla and left with his emerald half, Sonic-Zilla emerged and cried at his dead father's body in grief. Sonic-Zilla along with Espio-Zilla, Mighty-Zilla and Vector-Zilla are the only ones not to fight Giant Robotno despite Sonic-Zilla being present on Knothole Island. (SSS: #12)
- "Sonic-Zilla" is an obvious parody of the Toho monster Godzilla.