Neuro-Overrider
The Neuro-Overrider was a small computer-chip-like device invented by Rotor Walrus. It enabled the wearer to undergo the roboticization process but allowed that individual to retain his or her free will. The device was first meant to be used in a sabotage attempt on Robotropolis that involved roboticizing Princess Sally Acorn. Unfortunately it fell off her person and she became a slave to Dr. Ivo Robotnik until her later rescue. (StH: #29)
Sonic the Hedgehog later proposed a plan to let himself become a Robian while wearing one of the devices in order to destroy Robotropolis with an enhanced body, but it was rejected by Princess Sally on account of being too risky. Sonic was then Roboticized against his will, but even if approved, his plan would not have worked anyway. After Snively analyzed Sally's Neuro-Overrider and deduced its function, Robotnik upgraded all his Roboticizers with Brain-Burn-Thru software which assured complete control over all Robians, particularly Mecha Sonic. In order to combat Mecha Sonic when he attacked Knothole Village, Knuckles became Mecha Knuckles using a Neuro-Overrider and an old Roboticizer that did not have the Brain-Burn-Thru software so that he would not turn on the Knothole Freedom Fighters. (StH: #39, SMM)