Proto:Sonic the Hedgehog 3 - The Cutting Room Floor

Sonic the Hedgehog 3 (prototype; 1993-11-03)/Hidden content - Sonic Retro

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

Sonic 2 [Beta / Proto / Unused Stages - Mega Drive / Genesis] - Unseen64

Sonic Adventure Cutting Room Floor - Colaboratory

Sonic Style Sprites - Original and Custom v9 by Abbysek on DeviantArt

Proto:Sonic Heroes/E3 2003 prototype - The Cutting Room Floor

Early Sonic 3 prototype found, features major differences to the final game, Page 4

Proto:Sonic the Hedgehog (Genesis)/Green Hill Zone - The Cutting Room Floor

Sonic the Hedgehog (16-bit) (prototype)/Hidden content - Sonic Retro

Sonic The Hedghog 2: Beta Analysis - Unseen64

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

News/Sonic Month Part 5 - Before Hard Times - Sonic 3 (MD) - Hidden Palace

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

Proto:Sonic the Hedgehog 3 - The Cutting Room Floor