It’s Goku turning Super Saiyan, Sonic becoming Super Sonic ... Many games have played around with the horror of transformation, with these games being some of the best examples.

by far the biggest talking point is what appears to be a glimpse at an alternate timeline with Eggman ruling over Earth alongside Metal Sonic. In Sonic the Hedgehog 3's post-credits scene ...

an adventure title based on the Sonic the Hedgehog franchise, includes a myriad of playable characters and alternate skins. The Rockstar Sonic skin, an alternate outfit for Sonic, is the newest.