Sega's Sonic the Hedgehog is one of the gaming industry's most famous mascots and the character and franchise's immense popularity has even extended into successful live-action feature films. The Sonic the Hedgehog series has evolved in many ways far beyond its obvious transition from 2D to 3D. An expanding cast of friends has been a Sonic staple ever since Tails' introduction in Sonic the Hedgehog 2.
Source：https://www.cbr.com/shadow-the-hedgehog-differences-from-sonic-video-games-lore-trivia/
