After the original Miles Mays was killed by Dr. Checkburg (AKA Gizmo), he was sent to hell where he made an agreement with the Jewish Satan (he's like the red guy but actually scary). The agreement was that Miles Mays would live on Earth again, but would have to work hard to achieve it, then Jewish Satan created a new realm for Miles Mays, as well as the body of Tails (because his birthname was also Miles Mays) to partly control until he can reposses his own body.