Sonic the Werehog is Sonic the Hedgehog's bestial werewolf-like form in Sonic Unleashed. This form was created when Sonic accidentally absorbed a large dose of Dark Gaia's energies, though the transformation would be triggered when nighttime came and remain active until daytime began. Due to this form's unique traits, Sonic the Werehog is essentially a hedgehog/Dark Gaia's Minions hybrid. Sonic later lost this form permanently when Dark Gaia reclaimed the energies that caused the transformation.
When transformed, Sonic grows slightly taller and he gains much more muscle mass and weight. As a result, his chest gets broader, and his arms grows larger and out of proportion. His hands also get bigger and his nails become claws that he can use offensively. His muzzle grows larger as well and his teeth become sharp and pointy, making him resemble more that of a wolf. His ears also become more curved.