New Sonic the Hedgehog (1991) prototype uncovered by preservation groups - Tails' Channel

A prototype of Sonic the Hedgehog (1991) was showcased by a video game preservation group in a New Year's Eve livestream.

21 Crazy Facts About Sonic and the Console War He Started - IGN

Proto:Sonic the Hedgehog (Genesis) - The Cutting Room Floor

Adventures of Sonic Episode Reviews Newbie's Perspective – CrystalMaiden77

IDW Sonic Comic Reviews Issues 1-64 Newbie's Perspective: – CrystalMaiden77

Who would win in a fight, Godzilla or Sonic? - Quora

Sonic the Hedgehog 2 HD - Sonic Retro

21 Crazy Facts About Sonic and the Console War He Started - IGN

Here's A Look At The Official Prototype For Sonic The Hedgehog (1991)

Sonic the Hedgehog (2006), Sonic Wiki Zone

7 Sonic The Hedgehog Prototypes You Were Never Meant To Play