Sonic The Hedgehog 3 & Knuckles (lost build of cancelled iOS port of Sega Genesis platformers; 2014) - The Lost Media Wiki

Editing Sonic the Hedgehog 2006 (lost build of Tokyo Toy Show tech demo of multiplatform platformer; 2005) - The Lost Media Wiki

Sonic The Hedgehog: Awakening (lost build of cancelled Sonic the Hedgehog game; existence unconfirmed; late 2000s) - The Lost Media Wiki

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

Sonic 3D Blast - Wikipedia

ALL Sonic 3 & Knuckles Unused Content

Editing Mario & Sonic at the Sochi 2014 Olympic Winter Games (lost build of cancelled 3DS version of Wii U crossover sports/party game; existence unconfirmed; 2013) - The Lost Media Wiki

Sonic Adventure - Wikipedia

Sonic CD - Wikipedia

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

Shadow the Hedgehog (lost early build of platformer; 2005) - The Lost Media Wiki