As pointed out in the tweet below, Sonic is the only character to receive a sprite redesign when morphing into his 'Super' form. All other characters, including Tails, Knuckles, Mighty ...

Miles "Tails" Prower voice actor Colleen O'Shaughnessey will return to voice Sonic's sidekick in the live-action Sonic the Hedgehog 2 film. "Taking my old pal Tails for another adventure.