Board Thread:General Discussion/@comment-24270839-20131212055952/@comment-679780-20131227005616

My personal headcanon, which is obviously fanon given we played Sonic4: Metal ourselves, is that Modern Metal Sonic was Classic Metal Sonic before his restoration in Mad Gear Zone. Just sonic Team, for some reason, couldn't use Classic counterparts even when they were logically needed.

As for how Classics characters became Modern characters, I simply believe they grown a little and had a slight change of style.