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

Sonic 3 Prototype With Lost Content Discovered - IGN

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

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

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

In honor of this turd's 4th birthday, how would YOU re-write Sonic Forces into a good story? : r/SonicTheHedgehog

Brand new Sonic Heroes prototypes uncovered - Tails' Channel

Community – The Sonic Stadium

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

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

Sonic the Hedgehog (lost Winter Consumer Electronics Show 1991 demo build of Sega Genesis/Mega Drive platformer; 1991) - The Lost Media Wiki

Sonic the Hedgehog 2 - Wikipedia