Sega's Sonic the Hedgehog remains one of the most popular video game franchises of all time because of its willingness to take chances and embrace a wide world of supporting characters beyond Sonic himself. Shadow the Hedgehog, a villainous counterpart to Sonic, is first introduced in Sonic Adventure 2 and less than five years later he was already the star of his own spin-off game, Shadow the Hedgehog.
Source：https://www.cbr.com/shadow-the-hedgehog-cult-classic/
