SONIC IS A PERFECT EXAMPLE OF CHARACTER DESIGN EVOLUTION

Summary from the TLDR Design newsletter

Even though Sonic's design has evolved through various artists, from Yuji Uekawa's modern look in Sonic Adventure to interpretations by Aaron Hammerstrom and Tyson Hesse, it has maintained continuity. Each artist has added their own unique touch. There are still debates among fans about how much Sonic's design should diverge from Uekawa's original standard.