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.

Sonic the Hedgehog - Main Characters / Characters - TV Tropes

Knuckles the Echidna - Wikipedia

Sonic the Hedgehog/History and appearances (IDW), Sonic Wiki Zone

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

Sonic the Hedgehog (character), Ultimate Pop Culture Wiki

Sonic the Hedgehog 2 HD - Sonic Retro

Sonic the Hedgehog (1991) prototype discovered - The Independent Video Game Community

Discuss Everything About Sonic Wiki Zone

Adventures of Sonic Episode Reviews Newbie's Perspective – CrystalMaiden77

Sonic the Hedgehog (Prototype) LOST BITS Altered & Unused Content [TetraBitGaming]

Sonic the Hedgehog (lost Tokyo Toy Show prototype build of Sega Genesis/Mega Drive platformer; 1990) - The Lost Media Wiki