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An animation very similar to one used in Wing Fortress Zone when Sonic grabs the panels on the side of the ship. Compared to the one used the final game, this animation is vertical instead of horizontal.
An alternate black and white death frame, originally from the first Sonic the Hedgehog, but still goes unused.
An unused animation of Dr. Robotnik accidentally dropping Mega Mack on his own head in the boss battle of Chemical Plant Zone.
Robotnik laughing in the Death Egg Zone when Sonic takes damage during the Mecha Sonicbattle. As it is not entirely unused, all animations get frozen when Sonic dies as there are no Rings in sight. This does later appear in the 2013 version of the game, even when Sonic has no Rings.
Every 1024 frames, this platform will slowly rise up for 128 frames, float in the air, then come back down 128 frames later. The amount of time it floats in the air is 128 frames. The upper four bits can be used to offset when it starts to rise in the air. This object has been around since the Nick Arcade prototype.
Chemical Plant Zone
The blue bubble snakes have many subtypes that define their movement pattern and their length, which can be any number of segments between 1 and 16. However, only those that are six segments long are used, leaving all other subtypes unused (00-0F for jumping back and forth and 10-1F for jumping between the floor and ceiling).
Chemical Plant Zone
The amount of time that these platforms in Chemical Plant Zone can stay flipped is variable. However, the final game for the upper four bits are always set to 70.
A ball and spring object, which can be placed in Debug Mode. If a switch is placed near it and pressed, the ball will pop out and start rolling in whichever direction Sonic was facing when the object was placed. This was seen in the Simon Wai version of the game.
Oil Ocean Zone
The stoppers used in the final version of the game launch the player upwards. It will launch the player right if the object subtype is set to zero. This would have been used in the Simon Wai prototype, but it has no purpose in the final layout. They were later found in Sonic Mania.
A crystal which was used in the earliest two prototypes to block off a tube in Hidden Palace Zone. The graphics are no longer present, but the code is, and it functions like normal. It was later reused in the 2013 version of the game.
Hidden Palace Zone
Another Hidden Palace Zone leftover. Its graphics no longer exist. Placing one with a subtype greater than 17 will spawn garbage objects on the right. It was later added in the 2013 version.
A static monitor, which is also found in the original Sonic the Hedgehog, can be placed in Debug Mode. Destroying it will harm the player.
Seven leftover sounds from Sonic the Hedgehog are present in the game's files.
The sound of when the player hits the R, UP, or DOWN blocks in the Special Stage.
The electricity from Scrap Brain Zone.
An unused sound from the original Sonic the Hedgehog.
Hitting the colored diamonds in the Special Stage.
The warp noise made by a Giant Ring when Sonic enters it.
Chain pulling sound from the Marble Zone.
Bonus point tag appearing at the end of an act.
A low siren which is used in the 2-Player mode.
Seems to be a slightly shorter version of Mystic Cave Zone's bridges stopping in place.
Two clips of Hidden Palace are found within the game's files.
This song can be played in the Sound Test of #10.
This song can be heard in Sonic the Hedgehog 1 & 2 Soundtrack album. This is from an earlier demo version of the game.
Scrapped level remains
Six corrupted levels are found buried in the game's files that can be accessed via hacking.
Ocean Wind Zone
This stage is an objectless version of Emerald Hill Zone Act 1, along with the life counter having a Tails icon instead of Sonic's. Finishing Act 1 by hacking in an animal capsule will send the player to Emerald Hill Zone Act 1. It reuses Emerald Hill Zone's animals, Ricky and Flicky. The level also contains remnants of Labyrinth Zone from the Nick Arcade prototype.
Containing the original sprites from the prototype versions, this is another objectless level of another remnant to Emerald Hill Zone Act 1 but with Wood Zone's palettes, Metropolis Zone's music, and some glitched collision. The life counter is Tails' icon. Hacking a capsule into this Zone sends the player to Metropolis Zone.
Another empty stage and again takes place in Emerald Hill Zone Act 1. The Zone uses Oil Ocean Zone as its default music theme. Badnik sprites from Metropolis Zone and Emerald Hill Zone can be loaded, and finishing the level will send the player to Emerald Hill Zone Act 1.
The stage is heavily corrupted as all that remains is the main act logo and the use of track #10 from the Sound Test. When the player spawns, they immediately die as there is no collision in the level.
Another empty Zone using Emerald Hill Zone Act 1 again. This version of the stage uses garbled Emerald Hill Zone tiles. Badnik sprites from Oil Ocean Zone are loaded, has very little collision data. No objects are present within the debug menu, making it impossible to finish by any means. By hacking in an animal capsule, the player will go to Emerald Hill Zone Act 1.
Attempting to load this stage will cause the game to crash on the title card as no other code references it. It does reuse Sky Chase Zone's animals, Tocky and Cucky.
Unused score tally
A score tally showing the words, "Sonic/Tails got through Zone". The final game shows the text of "Sonic/Tails got through Act 1/Act 2" instead. This would later be used in Hidden Palace Zone in the 2013 re-release of the game.