Sonic the Hedgehog 2 (Genesis)/Oddities

This is a sub-page of Sonic the Hedgehog 2 (Genesis).

Special Stage Perfect Bonus

Much like in regular stages, Special Stages have a Perfect Bonus programmed to be awarded when you collect all the rings. While present and fully functional, actually getting a Perfect Bonus can only be described as a herculean task: it requires the "Sonic and Tails" mode to collect the rings Sonic's hitbox alone can't reach, along with a ludicrous amount of coordination and memorization of the stages by two players thanks to the unusually difficult level design and loose ring placement.

• Perfect Bonuses for Stages 1, 3, and 6 have been successfully TASed.
• Stages 2 and 4 are believed to be impossible due to strange collision, with the former having issues in its second section (despite it looking trivial) and the latter having a 5-deep triangle of rings at its very end that can't be fully collected.
• Stage 5 is believed to be impossible due to Sonic and Tails being unable to reach some of the rings in time (in the first section alone, there are simultaneous 4-deep ring triangles on opposite walls).
• Stage 7 is downright impossible thanks to its third section's random-scatter of a ring pattern.

Special Stage Ring Requirements

On a related note, although each Special Stage has three segments, the table that determines what the next ring requirement should be has an additional entry for each one; below are the unused entries. Whether there was a planned fourth segment for each Special Stage or if they were just to pad out the table for alignment purposes is unknown, although they were strangely updated in Knuckles in Sonic 2.

Unused Ring Requirements

	Stage 1		Stage 2		Stage 3		Stage 4		Stage 5		Stage 6		Stage 7
Sonic and Tails	120		150		170		160		200		220		210
Sonic/Tails Alone	110		140		160		150		160		210		190
Knuckles in Sonic 2	110		130		160		150		130		170		140

Inaccessible Rings

Some levels have rings in places that cannot be reached, making a Perfect Bonus impossible.

Location Image	Level	Approximate Coordinates	Description	Location Image (Prototype)
	Aquatic Ruin Zone Act 2	1FA90626	Two rings lined up horizontally. The rightmost can actually be touched without going inside the pillar, but there's no way to reach it. The pillars weren't there prior to Beta 5, allowing the rings to be collected.
	Casino Night Zone Act 2	027F00F8	Two clusters with seven rings each, just above the start, but way too high to reach. These rings have mysteriously been transported from Act 1 to Act 2, this same problem also occurs with the rows of rings that should be from a launcher. These rings would be easily reached using fippers that are centered just below the rings. When locked-on to Sonic & Knuckles, it is possible for Knuckles to collect these rings by gliding to the far left from the highest wall. In the September 14 prototype, these flippers could be used to reach the enigmatic rings on Act 1. These rings were removed in the the 2013 remake.
	Casino Night Zone Act 2	10700611	It may seem strange, but this row of rings should be in Act 1; the level design fits perfectly where a ramp leads to a vertical launcher. This failure has been present since the September 14 prototype.
	Mystic Cave Zone Act 2	0F2B00F0	These may have been placed with the original level layout from the Simon Wai prototype in mind. In the same coordinates in that prototype is a tall pillar.
	Mystic Cave Zone Act 2	15880160	These may have been placed with the original level layout from the Simon Wai prototype in mind.
	Mystic Cave Zone Act 2	16050156	These rings may have been part of the original level layout for this Zone in the Simon Wai prototype. As there is a ledge and an empty space in the same coordinates in that prototype, a swinging platform may have been in these coordinates to accompany the rings.
	Oil Ocean Zone Act 2	0BC003A8	These are leftovers from the original level layout seen in the Simon Wai prototype. The same rings can be found in the same coordinates in that prototype.
	Oil Ocean Zone Act 2	11BF023A	These are leftovers from the original level layout seen in the Simon Wai prototype. The same rings can be found in the same coordinates in that prototype.
	Oil Ocean Zone Act 2	12C0023A	These are leftovers from the original level layout seen in the Simon Wai prototype. The same rings can be found in the same coordinates in that prototype.
	Oil Ocean Zone Act 2	191001F8	These are leftovers from the original level layout seen in the Simon Wai prototype. The same rings can be found in the same coordinates in that prototype.
	Oil Ocean Zone Act 2	1A0001F8	These are leftovers from the original level layout seen in the Simon Wai prototype. The same rings can be found in the same coordinates in that prototype.
	Oil Ocean Zone Act 2	20880300	These are leftovers from the original level layout seen in the Simon Wai prototype. The same rings can be found in the same coordinates in that prototype.
	Metropolis Zone Act 2	02C0043F	Three horizontal slanted rings, under the floor with the ten-ring box and a cog nearby. This floor used to be a slope in the Simon Wai prototype, so these rings may have been placed with the slope in mind.
	Metropolis Zone Act 2	135000D0	These rings may have corresponded with the original level layout from the August 21 prototype. Judging by the layout in that build, these rings could have been reached by jumping from the nearby conveyor belt.
	Metropolis Zone Act 2	0F000169	These rings appear to correspond with the original level layout from the Simon Wai prototype. There is a ledge in the same coordinates in that prototype, so the rings may have been placed on top of it.
	Metropolis Zone Act 2	0F400354	These rings appear to correspond with the original level layout from the August 21 prototype. In the same coordinates, they would have been under a ceiling.

Misplaced Objects

Various objects throughout the levels are misplaced or in odd positions, possibly indicative of earlier level designs.

Image	Level	Approximate Coordinates	Description
	Aquatic Ruin Zone Act 2	08E606CC	A misplaced air bubble object.
	Hill Top Zone Act 1	128A020C	This poor seesaw was overlooked once the layout was altered from the Simon Wai prototype.
	Metropolis Zone Act 3	0A89026C	This object, found next to an invincibility monitor, is a set of horizontal spikes, for which the graphics are never loaded in this Zone. It serves the practical purpose of preventing zipping bugs.
	Metropolis Zone Act 3	116905AC	A door object with no use or any real reason to exist. This fits with the August 21st prototype's layout.
	Metropolis Zone Act 3	1D1F054D	A platform that moves if Sonic is underneath it. This fits with the Simon Wai and August 21st prototype's layouts.
	Metropolis Zone Act 3	1F75056C	Either a lava pit was intended to be here, or this is another anti-glitch trick. This fits with the August 21 prototype's layout.

CPZ/DEZ Door

In-Game	Corrected

The door sprite in Chemical Plant Zone and Death Egg Zone is actually assembled incorrectly. By using Debug Mode to place a door, you can see how the door's sprite is supposed to be assembled, using 8×8 tiles that go unused due to the incorrect sprite assembly. The reason for this is because the doors use the object subtype $00, the subtype meant to be used by the doors in Hill Top Zone, rather than subtype $02 which is meant to be used in Chemical Plant and Death Egg.

The 2013 rerelease uses the correct sprite for the doors, and Chemical Plant in Sonic Mania also uses the correct appearance.

Duplicate Rings

A column of rings found next to a giant cog at coordinates 08F005E8 if you take the path to the right after the first yellow spring shaft in Metropolis Zone Act 2 is very unusual: Each ring collected gives you four rings instead of one, for a total of 12 rings. This is because these rings are actually four columns of rings that are all laid out on top of each other in the same coordinates. This oddity is still there in the 2013 remake.

Early Wing Fortress Zone

A small piece of Wing Fortress Zone appears in Sky Chase Zone, but not all of it is visible because of how the stage scrolls.

This Wing Fortress has several differences from the actual stage version: some windows were removed and others added, the rivets are placed differently, there is a long metal frame on the left, and a small platform exists near the propellers on the lower right.

Wing Fortress Weirdness

Wing Fortress Zone, being added very late in development, has the most strangeness of any stages in the game:

• Near the end, there is a conveyor belt that should move Sonic accordingly; however, due to an incorrect subtype value for the conveyor object, it does nothing. Even if it was correct, it would still stop halfway.
• Shortly before the conveyor belt is a random suspended cable with no obvious purpose. Presumably, the intent was to have a moving platform holding onto it (similar to Hill Top Zone), but it got scrapped and instead the player gets across using speed boosters.
• The boss completely lacks sound effects, barring the explosion sequence.

Programming Oddities

• Each variation of the generic menus (1P/2P level select and Options menus) use a separate jump command when loaded in the "game mode index" (set using value $FFF600), despite the fact that they all jump to the same location.
• Similarly, the game has two instances of the code used to display a 512×512 plane mapping - one for the Special Stage, the other for the Sega screen - but both are identical.
• The graphics data for Mecha Sonic is loaded on the Sega screen right before it gets overwritten with the upscaled Sonic graphics. The reason for this is unknown, although it's possible the graphics were used as a placeholder before the upscaling logic was added.
• The Sega screen is programmed to play the "SE-GA!" sound twice, although the second instance (in the Sega screen logic itself) never gets played due to engine limitations. This is a leftover from Sonic 1, which did the same thing as it didn't have any objects on the screen.