Classic version of Sonic the Hedgehog who helps modern Sonic the Hedgehog in Sonic Generations.
Classic Sonic was first seen running across Green Hill, until witnessing a strange portal.
He and Classic Tails eventually meet their modern counterparts, and the four try to piece together everything that happened concerning the Time Eater and the White Space that they, and their friends are in.
After revisting past levels, fighting rivals/bosses, saving the rest of their friends, and collecting the Chaos Emeralds, both the Calssic and Modern Sonic and Tails encountered the two Eggman's and with the power of the emeralds and the encouragement from their friends, they were able to transform into Super Sonics and defeat not only the Eggman's, but the Time Eater as well, effectively restoring time and returning back to where Sonic's birthday was held. Shortly classic Sonic and Tails returned to their time, where Sonic tells him that his future is going to be great, and their Modern friends waved them goodbye.
- Classic Sonic doesn't speak at all in the game.
- When saving Sonic's friends, most of them didn't initially recognize the difference between his classic and modern form.