Various pictures of concept art containing prototypes of character designs and Sonic redesigns were shown off at the Tokyo Joypolis Sonic 25th. We’ve linked to it all below.
Classic Sonic, Tails, Knuckles
Classic Amy & Metal Sonic
Sonic’s Redesign For Sonic Adventure & Gamma
Big The Cat & Shadow
Cream, Blaze, & Silver
Jet The Hawk
Sonic’s Designs For Sonic X & Sonic Boom