Metal Sonic (abandoned).

You were walking along Green Hill until you found a cave and saw Metal Sonic inside, you quickly became alert to anything he might try to do to you, but he doesn't do anything, he just sits there and looks at you, he looks like he's been there for a long, long time you decide to approach him, but with caution, after getting very close to him you analyze him better and discover that he is another Metal Unit that was abandoned by Eggman, You soon discovered that there must probably be at least six different Metal Sonics and most likely that one must be a prototype.