Sonic the Hedgehog (Genesis)

Sonic the Hedgehog
Developer: Sonic Team Publisher: Sega Platform: Genesis Released in JP: July 26, 1991 Released in US: June 23, 1991 Released in EU: June 23, 1991 This game has unused enemies. This game has unused graphics. This game has unused items. This game has debugging material. This game has a hidden sound test. This game has regional differences. This game has a prototype article This game has a bugs page This game has a prerelease article

Sonic the Hedgehog is more or less the definitive game of the Genesis in the early '90's.

Level Select

The code to unlock this game's level select is one of the most well-known codes in gaming history. Just press Up, Down, Left, Right on the title screen and you will hear the game's ring-pickup sound. Hold A and press Start to access the level select, and from there, you can choose any level or listen to the sound test. In early versions of the game, the level order is different from the order in normal gameplay.

Debug Mode

This is another well-known code. Up, C, Down, C, Left, C, Right, C is the most common version of this code... however, the shortest version is C, C, Up, Down, Left, Right. You will hear a tone if it was entered correctly. Hold A, then press Start, and hold A until the level actually loads.

From here, you have access to a variety of things:

• Invincibility
• Infinite Time
• Debug Coordinates (In place of score)
• Sprite Counter (In place of time)
• Placement Mode: Press B during the game to enter it. From there...
  • Press A to move forward one object.
  • Hold A and press C to move backward one object.
  • Press C to place the object.
• Pause Options
  • Press A to go back to the title screen.
  • Press B to enable slow motion.
  • Press C to enable frame advance.

Unused Artwork

Special Stage Art

Note:All of these items can be seen in-game by using the debug mode to fall outside the playing area of the special stage. It is easier to see them when advancing frame-by-frame by pausing and pressing C.

Artwork	Name	Description
File:Sprite03.png	"Zone" Icons	Found in the object list for the special stages, and its graphics found in the ROM, these unused special stage icons have no known use. They are labeled for Zones 1-6, suggesting that they may have warped Sonic to another Zone from within the special stage as a sort of shortcut. They are solid, like normal blocks.
File:Sprite01.gif	1-up Icon	Extra life icon for the special stages. It is listed in the manual for the game, but it never actually appears in any of the special stages. It is, however, fully functional, and can be placed in any special stage. The icon disappears like a ring when touched.
File:Sprite02.gif	"W" Icon	An icon with the letter W on it. Its use is unknown, and it has no function when placed in-game. This block is solid.

Unused Monitors

Artwork	Name	Description
	Robotnik monitor	Does nothing. Is likely intended to hurt the player, as it does in the 16-bit Sonic the Hedgehog 2's 2-player mode.
File:Tv goggles.png	Goggles monitor	Does nothing. This is most likely accompanied by the unused goggle graphics. This may have provided the ability to breathe underwater.
	Static monitor	Does nothing. This is found in various areas of Scrap Brain Zone the player can not normally access, such as inside walls. It is possible to break one of them, however, by "digging" into the wall in a jump and popping it (the image of the monitor being a portion of the "zappers").
	"S" monitor	Does nothing. This monitor also appears in Sonic CD prototype 510, where it grants the player both extra speed and invincibility. That is most likely the intended function of the monitor here, as a Computer & Video Games issue alludes to a powerup which grants extra speed and invincibility. This suggests that the S monitors were functional at that point in development.

Unused Sonic Sprites

Artwork	Description
	This sprite shows Sonic standing while gasping for air. This was presumably used in Labyrinth Zone.
	This animation shows Sonic holding his breath while running. It is speculated that this was used during the countdown to signify no air is left for Sonic.
	This unused sliding sprite is similar to the one used in Sonic CD's Wacky Workbench Zone.
	As seen in a couple of prototype screenshots in magazines, Sonic appears to be striking a victory pose after passing the sign post.
	These Spin Dash-esque sprites are present in the final ROM, but their use is unknown. Some theories are that they were used for a move similar to the Spin Dash or that they are animations for some sort of warp movement, perhaps through winding tunnels. It's also possible that a teleporter like the one found in the 8-bit version of Scrap Brain Zone would have played the animation.
	This set of sprites showing Sonic falling or shrinking are not used in the game. While their intended use is unknown, they could have been used to simulate falling in the death animation. They may have also been used for a speed tunnel that would extend into the background.

Zone-Specific Art

Artwork	Zone	Description
	Green Hill Zone	The checkered ball seen on the Green Hill Zone Boss appears to have been originally used in Green Hill Zone, as magazine pictures have shown Sonic riding down hills on it.
	Green Hill Zone	The two faces pictured here are not in their original palette, but these appear to be an earlier version of the faces on the totem poles of Green Hill Zone.
	Green Hill Zone	These unused tiles were found in Green Hill Zone's tileset, and appear similar to the areas used in the underground areas of the 8-bit Sonic the Hedgehog's GHZ. These may have also been used for a cut underground area.
	Marble Zone	These spikes are horizontal, rather than the vertical spikes used in the final Marble Zone. They are also slightly thinner. They are fully working by placing them, though.
File:Letsgo.png	Spring Yard Zone	This unused graphic can be found in the tileset for Spring Yard Zone. It is unused in the final game, and can be found in several prototype screenshots shown in magazine previews.
	Labyrinth Zone & Scrap Brain Zone	This is a horizontal sprite of the Burrobot.
	Star Light Zone	These lights were found in Star Light Zone's data but not used.
	Star Light Zone	The three machines shown were found in Star Light Zone's dataset, but not used in the final game. They appear to have been background objects rather than obstacles.
	Final Zone	The left image shows the back of Robotnik's legs which can't be seen normally. The right image is what is normally seen.
File:RSBUD.PNG	Ending	Bumper that appears to be a rosebud with an incorrect palette. The ending level shares its debug item list with the Special Stage, so the bumper is usable in both.

Press Start Button

Many early previews of Sonic the Hedgehog showed the text 'Press Start Button' on the Title screen. In the final version it does not show up due to a in-game bug, but the graphics can be found inside the ROM. It is also possible to get them to display in the Japanese version. It appears after accessing the secret credits screen via a cheat code (in emulators, the region of the emulator must be set to Japan). An easier way to get it to appear is to enter the Game Genie code AB3A-DADV. You can also fix this bug by using a disassembly of the ROM.

Splats the Bunny

Splats is a prototype badnik from Sonic the Hedgehog which was cut from the final game. Despite not appearing in the game, the badnik appeared in a set of promotional trading cards for the game, was shown on the box of a series of Japanese Sonic figures, and was featured in the UK Sonic the Comic. When the Nemesis compression format was finally cracked in 2002, the sprites were discovered in Sonic 1.

Some controversy has broken out over the true coloring of Splats—though the sprites to the left have Sonic's palette applied to them and the trading card scan appears to have a bluish tint, the quality and validity of the card has been called into question. Other theories to his coloring include purple (for Spring Yard Zone's palette) and green (for Star Light Zone's second palette line.)

Goggles

The graphics were found hidden in the ROM. While the actual purpose of the goggles is unknown, it is speculated that they were meant to give Sonic the ability to breathe underwater.

Each frame of the graphic fits together with one of Sonic's poses. For example:

Unused Eggman Graphics

These graphics were found buried in the ROM. Their purpose is unknown, but it is speculated that they may be part of an "alternate ending sequence" in which Eggman explodes in the background while Sonic runs across the ending level in victory.

Invisible Credits

This is used in the game, but it is invisible due to the palette for the credits being black. With a palette editor, they can be made visible again. Alternatively, with the region set to Japan, press C, C, C, C, C, C, Up, Down, Down, Down, Left, and Right. Then, when the demo starts, hold Down, A, B, and C.

The credits translate to:

Position	Person
Program	Naka Yuuji
Plan	Yasuhara Hirokazu
Design	Ooshima Naoto Ishiwatari Jina Kataoka Rieko
Sound Produce	Nakamura Masato
Sound Program	Kubota Hiroshi Makino Yukifumi

Regional Differences

The clouds move faster from right to left at the title screen in the Japanese Version. The clouds in Green Hill Zone move from right to left in the Japanese Version.

(Source: Sonic Retro)