- For other characters by this name, see Mecha Sonic (disambiguation).
Mecha Sonic first appeared after Sonic failed to convince the other Knothole Freedom Fighters to allow him to be roboticized with a Neuro-Overrider device so as to increase his ability to fight Dr. Robotnik and thus ensure his enemy's defeat. Frustrated, Sonic left the group and headed for the Knothole gym, only to be ambushed and knocked unconscious by his old enemy Nack the Weasel, who delivered him to Robotnik in revenge for Sonic's role in his previous capture. Unable to escape, Sonic was then placed in a Roboticizer and transformed into Robotnik's obedient, super-powered slave with orders to destroy Knothole and the Freedom Fighters. After handily destroying a giant Crabmeat, one of Robotnik's earlier creations, Mecha Sonic flew to the Great Forest and engaged the Freedom Fighters in battle. Despite his old friends' clever countermeasures, Mecha Sonic proved a virtually unstoppable opponent; even Bunnie Rabbot and Knuckles the Echidna failed to stop him. (StH: #39)
It was only after Knuckles himself submitted to roboticization with a Neuro-Overrider in place to maintain his free will that a foe emerged who could challenge Mecha Sonic: Mecha Knuckles. The two engaged in an explosive battle in which much of Knothole and then Robotropolis was leveled, the latter when they crashed into a stockpile of nuclear warheads. Mecha Sonic was left damaged and near death by the blast, and his Mobian personality, which had broken through somewhat before when he had been ordered to destroy Knothole, reasserted itself. Due to the energies of the One Billionth Ring Sonic had collected, his personality remained intact despite the roboticization, and out of guilt for his actions he asked his friends to let him die. Unwilling to do so, Sally Acorn and her computer NICOLE initiated a process that restored Sonic to his healed Mobian form. (SMM)
Following these events, Sonic was tried for treason, as the Freedom Fighters believed that he had disobeyed orders and gone through with the plan anyway. However, after a trip to the Robo Hobo Jungle and finding out where Nack the Weasel was hiding from a group of Badniks, Sonic managed to apprehend Nack and the charges against him were dropped. Subsequently, Robotnik would use Mecha Sonic's design specs as the basis for one of his robots: the original Silver Sonic. (StH: #40, SQ: #3)
Later, Sonic and Tails were abducted by the Bem along with Dr. Eggman and Snively Robotnik, the former pair undergoing a roboticization that allowed them to retain their personalities while the latter two were restored to biological forms. The new Mecha Sonic and Mecha Tails were then pitted against their enemies to determine which of them was superior, the stakes being restoration to their previous forms or being trapped in their new forms forever. Unsurprisingly, the Mecha Freedom Fighters overcame their opponents, and thus were restored to their normal states. (StH: #118)
In the altered reality created by his and Dr. Albert W. Wily's use of the Genesis Wave, Dr. Eggman envisioned a version of Mecha Sonic who would serve him alongside Mecha Sally once the Super Genesis Wave rewrote all of reality. (StH: #251)
Mecha Sonic commanded Sonic's speed and strength enhanced to incredible levels, as well as granting him a small arsenal of weapons. Both Mecha Sonics could also fly and produce laser beams from their eyes, while the original could electrocute opponents. The original Mecha Sonic had powerful lasers built into his arms, while the second could launch rockets or nets. As robots, Mecha Sonic also commanded optic sensors equipped with heat-seeking and other features, allowing them to lock onto enemies much more effectively than Sonic's biological eyes.
Though the second version of Mecha Sonic had the same personality as the normal Sonic, the first Mecha Sonic had a second personality that was altered by Robotnik's Brain-Burn-Thru software which suppressed his normal one for the most part. This personality was unfailingly loyal to Robotnik, and possessed a vehement hatred for the Freedom Fighters. Mecha Sonic also seemed to possess some of Sonic's traits grossly distorted, with his overly healthy ego becoming ruthless arrogance. However, Sonic's true personality resisted the programmed one, which eventually led to his restoration.
- "Mecha Sonic" is the name used for the larger robotic Sonics that aren't Metal Sonic in the video games. However, due to lack of information over these names, the ones that showed up in Sonic the Hedgehog 2 and Sonic Adventure are referred to as Silver Sonic in the comics due to their silver bodies. It is highly possible that the Mecha Sonic from Sonic and Knuckles is the basis of the roboticized Sonic.
- One of Sonic's counterparts from an alternate dimension, Cyborg Sonic, is a partially roboticized version of Sonic and thus could be considered part Mecha Sonic.
- Mecha Sonic's appearance during the Bem's experiment differs slightly from the original design featured in Mecha Madness. Aside from being colored completely silver as opposed his original blue and yellow colors, the torso lacks the original belt and chest plates, as well as a redesigned head made to represent his Sonic Adventure-style design with longer spines.
- According to promotional art made by "Spaz" in STH: 86, Mecha Sonic had a more powerful form called Hyper Metal Sonic. Hyper Metal Sonic was also the name for Metal Sonic in Sonic the Hedgehog: The Movie.