Silver Sonic MK II is one of the many robots created by Doctor Eggman that are based off Sonic the Hedgehog. Its only appearance in the games was in Sonic Adventure, in which it can be seen in a stasis tube near the entrance to Eggman's Final Egg base. It is about twice the size of Sonic. It was unnamed in its game appearance, although it later appeared in the Archie Comics series and was given the name Silver Sonic MK II. Although many fans presume that he is a villain, his affiliation could not be considered evil, as he was never activated. His fate is unknown, but it could be presumed that he remains unactivated in the Final Egg base.
As stated above, the robot only appears in Sonic Adventure and its enhanced port Sonic Adventure DX: Director's Cut, where it is seen inside a stasis tube near Gamma's birth area. It also appeared in the Archie Comics later on.
In Sonic Adventure, and it's remake Sonic Adventure DX, Silver Sonic MK II can be spotted inside a storage tube near Gamma's birth area. Though it plays no important role in the story, he has a cameo role in Gamma's. When Gamma is awakened, he looks around the room, spotting Metal Sonic and Silver Sonic MK II. Though it is obvious that Metal Sonic was set free at some point, it is largely unknown what happened to this robot, or what was Eggman's purposes to create it.
In the Sonic the Hedgehog series published by Archie Comics, Silver Sonic II was a scaled-down version of Silver Sonic and a part of the Metal Sonic Series. After the defeat of Perfect Chaos in Station Square, Eggman unleashed Silver Sonic II to attack the vulnerable city. The robot's power proved to be too much for most of the Freedom Fighters, but he was defeated by Sonic, who knocked his head off. He was then reprogrammed and repaired by Nate Morgan to act as the city's defender against Eggman and outside forces of evil.
When Eggman went to retrieve Silver Sonic II's body and repair him, he was chased out of the city. Silver Sonic II chased Eggman all the way to the remote Prison Island, where Eggman fell down a deep hole and was presumed killed. (In fact, Eggman survived, having stumbled onto his grandfather Gerald's laboratory.)
Three months later, when Shadow the Hedgehog came to Station Square to steal the Chaos Emerald located in their bank's safe, Silver Sonic II attempted to stop him. Unfortunately, Shadow used his Chaos Control powers and destroyed the city's defender. Silver Sonic II's remains were picked up by detective J.J. Moto, and the robot has not reappeared since (it could be presumed that he is undergoing reconstruction).
- In a texture hack for Sonic Adventure, one could swap Metal Sonic with Silver Sonic MK II, tough there is no difference in gameplay.
- Silver Sonic II is, to date, the only Sonic look-a-like to appear in a game (or two if one counts the Director's cut to be a separate game) to not be fought as a boss or be a playable character (in an official sonic game).
- Since the robot went on without a name at all in it's original appearance, fans and players have called it "Mecha Sonic", however the Archie comics later on named the robot Silver Sonic II which has since become it's primary name though some still prefer to call it "Mecha Sonic".
- It's notable that within all of the classic era, all Sonic themed robots (in the original manuals) were called Mecha Sonic, including the actual Mecha Sonic, the original Silver Sonic and Metal Sonic.
- This can bring up a question as to whether or not "Silver Sonic II" would have been the actual intent of the original game designers to be the robot's name, but nonetheless it is still the robot's most common name and can be considered the most official.
- It can be noted that Silver Sonic II's weapons were only showcased in the Archie Comics appearances he had, which of course means that whether or not he would have these abilities within the games has yet to be seen.
- Silver Sonic II at Mobius Encyclopedia, the Archie Sonic wiki