Zentendo: "In recent days, Sonic the Hedgehog has fallen on hard times, with almost all 3D iterations of the franchise being met with universal disappointment. There have been some brilliant 2D games, but the home-console versions have always been nothing but lacklustre. The last really solid Sonic game was on the Nintendo Gamecube, with Sonic Adventure Battle 2. Sonic Unleashed takes Sonic in an unfamiliar direction: a solid 3D Sonic title.
Whilst this happens, Sonic is sent flying down to the planet below, and as a direct result of the interference of Eggman, Sonic's had some form of mutation that transforms him from his standard Sonic appearance into a Werehog during the night. Once he's crash landed he bumps into a creature named Chip who has lost his memory, but Sonic and him pair up and start to look for ways to repair the planet."