Rouge the Bat
The most glaring difference between Sonic the Hedgehog 3 and Sonic Adventure 2 is the absence of Rouge the Bat. The Dreamcast game had two dueling stories: Hero and Dark. The Hero story followed Sonic, Tails, and Knuckles as they attempted to thwart Eggman’s latest plan to rule the world, while the Dark side followed Eggman’s story alongside those of two new companions: the Ultimate Lifeform Shadow the Hedgehog, and a double agent government spy named Rouge the Bat. Rouge has yet to appear in the live-action universe, but she acts as Knuckles’ rival and Shadow’s teammate in the video game continuity. Elements of her story in Sonic Adventure 2 still exist in Sonic 3, with the heist segment in the second act an obvious stand-in for her level Security Hall, but there’s no sign of the treasure hunter in the movie itself.
There have been reports that Paramount plans to give Shadow his own spin-off, and since Rouge didn’t show up in the movie based on her debut game, this would be the most logical place for her to appear next.
