Found by contributors here and The Cutting Room Floor.
|Green Hill Zone||Totem Pole||Not really lost in the Master System game as it is used there, but it is unused in the Game Gear version, yet the graphics still exist there.|
|Green Hill Zone||Green Hill tile||Just a corner piece from the Master System version.|
|Green Hill Zone||Green Hill tiles||Checkered spike from the Game Gear version of the game.|
|Bridge Zone||Ground segment||This appears amongst the object tiles for Bridge Zone, in both the Game Gear and Master System versions. It almost looks like the top is melted.|
|Bridge Zone||Bridge Zone tiles||Spring in front of checkerboard pattern, and pole in front of sky tiles. The bridges in this zone are do not reach sky level. Found in both versions.|
|Jungle Zone||Spring||A spring without grass present. Probably meant for Act 2. Found in both versions.|
|Labyrinth Zone||Door (?)||This appears amongst the object tiles for Labyrinth Zone, in both the Game Gear and Master System versions. Perhaps it was intended to be a switch-operated door, like the ones in the Genesis version.|
|Labyrinth Zone||Giant Pillars||Small and big pillars. No pillars like these exist in the 16-bit version of the level. Found in both versions of the game.|
|Sky Base Zone||Sky Base Act 3 tiles||Slopes and laser turrets. The latter tiles are not in the Game Gear version.|
|Sky Base Zone||Sky Base tiles||Chain facing and unused cannon facing .|
|N/A||Shield||This may be a prototype shield animation. This is similar to the shield animation used in Knuckles' Chaotix.|
|Green Hill Zone||Unused Enemy||KT15 found unused sprites in Green Hill Zone. These two animations are unused, however, another animation is used, but it is used in Jungle Zone, not Green Hill. This sprite is only found in the Master System version of the game.|
|Marble Zone||Unused Enemy||This Bat sprite appears in Green Hill Zone but isn't used. It was probably meant to be in the caves of Act 2. In the 16-bit version this is a normal enemy in Marble Zone, a level not found in this version. This sprite is only found in the Game Gear version of the game. An 8-bit remix of the Marble Zone music was discovered in the game, which means that Marble Zone was possibly a playable level at some point, and it's a possibility that this enemy could have been used in the level.|
An 8-bit rendition of the Marble Zone music is present at $CD0A in the Sega Master System ROM. This and the unused Bat Sprite provide evidence that Marble Zone was probably meant to be in the game, but was cut at some point. A ROM image with Green Hill Zone's music replaced with the Marble Zone music is available here.
Ancient handled the 8-bit port of Sonic the Hedgehog and it looks like they intended to credit themselves on the title screen as can be seen from this VRAM window. However, they left this out totally and in the end only Sega received the credit on the Title Screen. If it were used it probably would have appeared on the bottom of the screen reading Sega/Ancient 1991.
|Sonic the Hedgehog (8-bit)|