Sonic the Hedgehog 2 (Sega Master System, Game Gear)

Sonic the Hedgehog 2
Developers: Aspect, Sega Publishers: Sega (JP/US/EU/AU), Tec Toy (BR), Samsung (KR) Platforms: Sega Master System, Game Gear Released in JP: November 21, 1992 (Game Gear) Released in US: November 17, 1992 (Game Gear) Released in EU: October 16, 1992 (Master System), October 29, 1992 (Game Gear) Released in AU: December 1, 1992 (Master System) Released in KR: 1992 (Master System) Released in BR: December 25, 1992 (Game Gear), June 18, 1993 (Master System) This game has hidden development-related text. This game has unused graphics. This game has unused items. This game has unused music. This game has a hidden level select. This game has regional differences. This game has revisional differences. This game has a prototype article This game has a prerelease article This game has a bugs page

To do: Apparently half of the title cards artwork in this game has palette oddities, as seen in this Twitter thread. Could there be more in the game?

The 8-bit Sonic the Hedgehog 2 has Tails practically everywhere except in the actual zones. It introduced the idea of fighting badniks as bosses and the requirement to unlock the final level.

This game also marks the first appearance of Tails in a video game, contrary to popular belief.

Sub-Pages

Prototype Info

Prerelease Info

Bugs

Version Differences A lot can change when porting to another console, then emulating it.

Level Select

Master System

While powering on the game, hold Left + 1 + 2 on Controller 2. When the intro sequence starts, release the buttons, then start the game as usual.

Game Gear

When the intro starts, hold Down + Left + 1 + 2 + Start. When the title screen appears, wait for a ring sound to play twice (Tails will wink three times). Release all the buttons and press Start.

Unused Graphics

Character Sprites

Artwork	Name	Description
	"Crying Tails" Animation	Tails crying. Probably meant to be used in the ending cutscene when he is rescued.
	"Bored Sonic" Animation	While the majority of the game's Sonic graphics were copied from the Master System version of Sonic 1, the waiting animation was changed, rendering these three frames unused. They were used in the AutoDemo prototype, though.
	Sonic 1 Death Sprite	Sonic's death sprite from the Master System Sonic 1. The final version uses an updated sprite.
	Under Ground Zone Boss body	The entire body of the boss. Normally, only its head is visible.
	Sky High Zone Boss body	The entire body of the boss. Normally, only its head and neck can be seen.

Monitors

Artwork	Name	Description
	Sonic Monitor	While you can find this in a wall in Crystal Egg Zone, the graphics are obscured. When collected, it grants a continue.
	Question Mark Monitor	May have given a random amount of rings or items, like in the 2-player mode of the Genesis version.
	Grey Sneaker Monitor	May have slowed you down, like the Speed-Down sneaker in the 2-player mode of Sonic 3.
	Arrow Monitor	Most likely intended to be a checkpoint marker, like the 8-bit versions of Sonic 1.

Level Art

To do: Aqua Lake Zone, Green Hills Zone, Gimmick Mountain Zone, Scrambled Egg Zone all have many unused tiles, as do Sky High Zone Act 2 and Crystal Egg Zone Acts 1 and 2.

Artwork	Name	Description
	Under Ground Zone Bricks	Several unused bricks. Tiles similar to the gray bricks were used in the AutoDemo prototype.
	Under Ground Zone Tunnel	Leftovers from the curved tunnels found in the AutoDemo prototype.
	Under Ground Zone rock	A 32×32 rock that was used in the AutoDemo prototype.
	Under Ground Zone Tiles	Miscellaneous unused pieces.
	Under Ground Zone Floating Platform	An unused floating platform.
	Sky High Zone boulder	This boulder was probably supposed to roll down a hill in Act 1.
	Sky High Zone platform	Another unused floating platform.
	Sky High Zone object	Unknown purpose - another platform?
	Sky High Zone water	Water tiles that were supposed to appear in Act 2. They look similar to the tiles found in the AutoDemo prototype.
	Sky High Zone trees	The trees from Act 1 were apparently supposed to appear in Act 2, but they don't.
	Sky High Zone background	A 32×32 background tile that was supposed to appear in Act 2.
	Aqua Lake Zone block	A small additional piece of land. If placed in Act 2, these are fully functional and cause Sonic to slide down much like Labyrinth Zone in Sonic 1.
	Aqua Lake Zone waterfall	This waterfall tile was probably going to be used with the block above.
	Aqua Lake Zone spikes	Unused spikes that were supposed to appear in Act 1 and 3. The only spikes found in this Zone are underwater.
	Green Hills Zone grass	While the miscolored grass tile on the left is used in-game, an unused, properly-colored grass tile exists.
	Green Hills Zone tiles	Unused graphics for background scenery that look like a flower stem.
	Green Hills Zone spring	A diagonal spring in front of the scenery that isn't used anywhere.
	Gimmick Mountain Zone breakable block	A breakable 32×32 tile that isn't used anywhere in the level.
	Scrambled Egg Zone breakable block	A breakable 32×32 tile that looks very similar to the Gimmick Mountain one, still unused.
	Crystal Egg Zone background tiles	Mountain background tiles that aren't used anywhere.
	Crystal Egg Zone tiles	Scenery tiles that aren't used anywhere.
	Crystal Egg Zone flower	An unused flower.

(Source: Sonic Retro, The Spriters Resource)

Screen Art

Artwork	Name	Description
	Early Title Screen	Leftover Title Screen used in the Auto Demo prototype found at addresses 0x206A0 to 0x213AF.

Gimmick Mountain Title Card

Originally, the level card for Gimmick Mountain Zone used its full name. Due to lack of space on the screen, however, "Mountain" was shortened to "Mt."

(Source: Hivebrain)

Unused Palette

Game Gear Version

In the Game Gear version, interestingly, there are some unused palettes and three of them are leftovers from the AutoDemo prototype!

Address	Palette	Description
0x26E45 to 0x26E64		A palette consisting of white, black, with various shades of gray. Possibly used as a test palette.
0x26E65 to 0x26E84		Used on the AutoDemo's Sega screen.
0x26E85 to 0x26EA4		Although not used here, this palette is used in the Level Select of Master System version and in the Unused Title Card of AutoDemo Prototype.
​​0x27005 to 0x27024		A palette for the Sega Logo to disappear.
​​0x271C5 to 0x271E3		Used on the AutoDemo's "Coming Soon" screen.

Master System Version

In the Master System version, strangely, both the test palette and the leftovers from the AutoDemo prototype are present. But, obviously, with Master System palette limitations.

Address	Palette	Description
0x2411F to 0x2412E		A palette consisting of white, black, and two shades of gray. Possibly used as a test palette.
0x2412F to 0x2413E		Used on the AutoDemo's Sega screen. But a little clearer due to limitations.
​​0x242DF to 0x242EE		Used on the AutoDemo's "Coming Soon" screen. But with a much more limited palette.

Unused Text

A build date string can be found in the ROM at 0x000C0.

Master System (REV00)	MS SONIC THE HEDGEHOG.2 Ver1.00 1992/09/05 SEGA /Aspect Co.,Ltd
Game Gear	GG SONIC THE HEDGEHOG.2 Ver1.10 1992/09/12 SEGA /Aspect Co.,Ltd
Master System (REV01)	MS SONIC THE HEDGEHOG.2 Ver2.20 1992/12/09 SEGA /Aspect Co.,Ltd

Unused Audio

Music

A peaceful, ethereal-sounding tune. What this song could have been used for is unknown, but it might have been an early theme for either Crystal Egg or Aqua Lake due to the similar style. The song also has some resemblance to the Present theme of Tidal Tempest in the Japanese/European soundtrack of Sonic CD. This song was removed from the Game Gear version, and was replaced by the sound effect that plays when Sonic (and Tails) look up at the stars at the end of the credits. Both of them use $92 as the song value.

Original Music Pitches

All tracks within both versions of the game are set to play at a semitone lower than they are actually programmed, though there are a few outliers by not just a semitones, but also an octave… or four. Please be aware that some of the internal keys set the pitch too high and may cause discomfort.

Song with internal pitch set	Restored version (if applicable)	Song name	Description
	N/A	Title Screen (Game Gear)/Opening Scene (Master System)
	N/A	Act Start	This one is interesting, in that all channels have their own key assigned. This is strange because this is something Mega Drive tracks tend to do, but not Master System/Game Gear tracks.
	N/A	Underground Zone
		Boss Theme (Master System)	Another track that has keys set for each channel. Reduced two octaves in restored version.
	N/A	Act Clear	Set one semitone lower in-game.
		Sky High Zone	Internally pitched too high. Reduced one octave in restored version.
	N/A	Invincible
	N/A	Aqua Lake Zone
		Power Sneakers (Master System)	Internally pitched way too high. Reduced four octaves in restored version.
	N/A	Green Hills Zone	Bears a resemblance to Sleeping Egg Zone from the Master System version of Sonic Chaos.
		Chaos Emerald	Internally pitched way too high. Reduced four octaves in restored version.
	N/A	Gimmick Mountain Zone
	N/A	Death
		Scrambled Egg Zone	Internally pitched too high. Reduced one octave in restored version.
	N/A	Boss (Game Gear)
		Bad Ending	Internally pitched way too high. Reduced four octaves in restored version.
	N/A	Crystal Egg Zone
		Good Ending	Internally pitched way too high. Reduced four octaves in restored version.
	N/A	The End (Game Gear)
	N/A	Unused Song (Master System)
	N/A	Game Over
	N/A	Continue

(Source: Original TCRF research)

Sound Effects

These were removed from the Game Gear version.

Sound Effect	ID	Description
	A7	Similar to the spring/ramp sound in the Autodemo.
	AC	Likely a fire sound.
	AD	An alternate splash sound.
	B2	Similar to Sound A2 from the Autodemo.

(Source: Original TCRF research)