Wirewolf

Like the Robotnik of SatAM and Robotnik Prime of the Archie continuity, Sonic Underground's Dr. Robotnik has already taken over most of Mobius. Like his counterpart, this Robotnik's greatest nemesis is Sonic the Hedgehog. However, he must also contend with Sonic's siblings, Sonia and Manic. Other than that, SU's Robotnik has a history much like that of SatAM's, including deposing the rightful ruler (SatAM's King Acorn, SU's Queen Aleena Hedgehog). Additionally, this version of Robotnik has the same design as the SatAM Robotnik, but wears a red cape rather than a yellow one. His voice was also different, performed by Gary Chalk who played Grounder from Adventures of Sonic the Hedgehog. Instead of Snively, who was not in the series, Robotnik's assistants were two canine bounty hunters named Sleet and Dingo.

This version of Robotnik did not appear in every episode, with Sleet and Dingo serving as the ever-present villains instead (as they were pursuing Sonic Underground while Robotnik remaind in Robotropolis). Unlike his SatAM counterpart, he did not Roboticise the whole population of Mobius; that was reserved for those who broke the laws (of which there were many), leaving an underclass for him to have fun oppressing and an aristocracy which he taxed heavily. While he is often viewed as less evil than his SatAM version, one of his goals is to find Sanctuary - where Freedom Fighter's leave their children - and exterminate all the children in it. He also once was willing to let the entire planet be destroyed by Chaos Energy if it meant the Sonic Underground would be destroyed as well.