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Sonic the Hedgehog (16-bit)/Hidden content

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Level select

Sonic1 level select.png

On the title screen, press Up Down Left Right. A ring sound will play - holding A+Start will bring up the menu, which also includes a sound test.

If running the Japanese game on a Japanese system, the code is Up Down Down Down Left Right, then A+Start.

This screen suggests the intended level order was different to what is seen in the final game, with every zone save for Green Hill Zone and Scrap Brain Zone (and Final Zone) changing positions. This order is reflected internally, as shown in the Action Replay codes at the bottom of this page.

Commentary found in the Sonic Jam strategy guide also confirms that Labyrinth Zone was originally intended to be the second zone but was moved due to its difficulty relative to Green Hill Zone.

Edit mode

Sonic1 MD Edit.png

On the title screen, press C C Up Down Left Right. A ring sound will play - holding A+Start until the title card appears will activate edit mode. Sonic will also be invincible.

If running the Japanese game on a Japanese system, the code is C C C C Up Down Down Down Left Right, then A+Start.

Due to a quirk in Sonic 1, other sources will give variations of this code. The game looks for two (or four) C presses during the sequence, but is not concerned about where they are placed - this means, for example, the hint in Sonic Jam, which specifies edit mode as UpCDownCLeftCRightC, A+Start is equally valid.

It is possible to activate both edit mode and the level select by separating the two codes (before A+Start) with an Up button press. Alternatively, activating edit mode, pausing during gameplay and pressing A will return to the title screen with the feature still activated.

Hidden Japanese credits

SonicTeamCredits.PNG

On the Sonic Team Presents screen, text showing the full names of key staff members and their roles in development is placed behind the Sonic Team Presents text. You cannot see this, however, because both the text and the background color are black.

With a cheat code, however, the game will hide the Sonic Team Presents text and change the background color to white, showing the hidden credits. In either ROM, with the region set to Japan, press C, C, C, C, C, C, Up, Down, Down, Down, Left, Right; you should hear a sound confirming this. Then, when the demo starts, hold Down + A + B + C and either press Start or wait for the demo to end. The Credits translated:

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

Staff roll and ending sequence from level select (Japanese version)

Up Down Down Down Left Right Up C C C C C C Up Down Down Down Left Right A+Start

Alternatively:

  • C C C C C C Up Down Down Down Left Right, wait until the demo starts, press Start to stop the demo, enter Zone Select cheat.
  • In the Sound Select, select 9E and press A/B/C to go to the Staff Roll, or select 9F and press A/B/C to go to the Ending Sequence (which will lead to the Staff Roll).

Misplaced objects

Crabmeat

Sonic1 MisplacedCrabmeat.png

There are multiple misplaced objects throughout the game. The above picture shows a misplaced Crabmeat in Green Hill Zone. It can be found at coordinates 10D0 0370.

Wall monitor

Sonic1 MD SBZ Act2HiddenMonitor.png

In Scrap Brain Zone act 2, a static monitor can be found inside a wall (above and to the right of a Super Ring monitor). It can be broken during normal play, but it does nothing. The graphics are largely obscured by the wall, but you can just about see the explosion and a corrupted tile when it is broken.

Missing shoe stripes

S1-floating.gif
Sonic1 MD Sprite SonicSpring.png

A couple of animations are missing the white stripes from Sonic's shoes. This could suggest stripes were added after much of the artwork was ready.

Unused content

Art

Sonic

Art Description
Standair.png
This sprite shows Sonic standing while gasping for air. This was presumably used in Labyrinth Zone.
Needair.gif
This animation shows Sonic holding his breath while running. It is speculated that this was used during the countdown to signify that Sonic must find air as soon as possible.
Slide.gif
This unused sliding sprite is similar to the one used in Sonic CD's Wacky Workbench Zone.
Victorypose.png
As seen in a couple of prototype screenshots in magazines, after passing a signpost Sonic would jump up and do a victory pose. This was removed before the final version, possibly because its use was complicated by the addition of post-singpost giant rings, which cause Sonic to disappear.
Spin.png
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.
Falling or shrinking.png
This set of sprites showing Sonic falling or shrinking are not used in the game, and their intended purpose is unknown. They might have been designed to simulate falling in the death animation, or for a speed tunnel that would extend into the background.
Sonic1 MD Sprite GreyDeath.png
A greyscale version of Sonic's death animation. His left foot is placed slightly differently.

Levels

Art Description
Totem.png
The two faces pictured here are not in their original palette, but they appear to be earlier versions of the faces on the totem poles of Green Hill Zone.
Missingghztiles1.gif
These unused tiles were found in Green Hill Zone's tileset and appear similar to the areas used in the underground areas of Sonic the Hedgehog (8-bit)'s Green Hill Zone. These may have also been used for a cut underground area.
Letsgo.png
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. The sign itself says "Let’s Go."
LZunusedswitch.png
An unused frame of the switch sprite. When bit 5 of a switch's subtype is set, it makes the object flash, using this sprite. In Labyrinth Zone, this sprite's data is partially overwritten by the cork sprite in VRAM. Marble Zone's switch has no equivalent sprite.
Burrobot1.png
This is a horizontal sprite of the Burrobot. Perhaps the Borrobot dug back into the ground after a certain amount of time?
Light.gif
Light2.gif
These lights were found in Star Light Zone's data but are not used.
Machine2.gif
Machinparts.png
The three machines shown were found in Star Light Zone's dataset but are not used in the final game. They appear to have been background objects rather than obstacles.
Robotniklegs1.png
The left image shows the back of Robotnik's legs, which can’t be seen normally. The right image is what is normally seen.
RSBUD.PNG
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.
Sonic1Gen UnkGrass.png
Unused section of grass which does not seem to match with any palette in the game.
Splats.png
Splats, a prototype badnik that was cut late in the game's development. Splats is unique in that it went on to be featured in merchandise and comic books, but only the art remains in the final game.
Goggles.png
Sonicgoggles Run.gif
Some yellow goggles, possibly intended for Labyrinth Zone. Each frame of the graphic fits together with one of Sonic's poses.
Altending.PNG
Unused graphics of Eggman exploding, possibly as part of an alternative ending sequence.

Special Stage

Note: All of these items can be seen in-game by using edit 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.

Art Description
Sprite03.png
Although these icons are found in the object list for the special stages and their graphics exist in the ROM, they are unused in the final game and have no known function; when placed, they act like normal solid blocks. They are labeled Zones 1–6, suggesting that they may have warped Sonic to another Zone from within the special stage as a sort of shortcut, or they were likely to indicate which Special Stage the player was in or which stage they came from after reaching the signpost.
Sprite01.gif
Extra life icon for the special stages. It is listed in the North American and European manuals for the gameMedia:Sonic1 MD US SonicJam manual.pdf[1]Media:Sonic1 MD EU manual.pdf[2], but it never actually appears in any of the special stages. It is, however, fully functional, and can be placed in any special stage; when touched, Sonic gains an extra life and the icon disappears like a ring.
Sprite02.gif
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. The Japanese often assocate the letter "W" with "double" which may give clues about its use.

Objects

Art Description
Tv eggman.png
Eggman monitor that does nothing. Is likely intended to hurt the player, as it does in Sonic the Hedgehog 2 (16-bit)'s 2-player mode. To add a functional Eggman monitor in the game see the SCHG page on how to add it.
Tv goggles.png
Goggle monitor nothing. Had it been used, it would most likely have been accompanied by the unused goggle graphics and may have provided the ability to breathe underwater. To add a monitor which adds a goggle Monitor that uses the goggle sprites, use this SCHG page.
Statictv.png
Static monitor that does nothing. This is found in various areas of Scrap Brain Zone that 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 is a portion of the ‘zappers’).
Tv super.png
"S" monitor that 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 an issue of Computer & Video Games alludes to a powerup which grants extra speed and invincibility. This suggests that the "S" monitors were functional at that point in development. In the 2013 remake it can be placed and once destroyed you transform into Super Sonic regardless of how many Chaos Emeralds you have.
Wreck.gif
The checkered ball seen on the Green Hill Zone Boss appears to have been originally used as a separate object in that zone, as magazine pictures have shown Sonic riding down hills on it. These can be seen in debug mode but not placed. Its associated code has been removed from the ROM.
Sidespike.png
These spikes are horizontal, rather than the vertical spikes used in the final Marble Zone, and are also slightly thinner. However, they can be placed and are fully functional. The object ID is 45 in SonED2.
PressStart.png
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 an 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: this occurs after accessing the secret credits screen via a cheat code (in emulators, the region of the emulator must be set to Japan), or an easier way is to enter the Game Genie code AB3A-DADV.
UnusedSwingingWreckingBallGHZ.png
The swinging platforms of Green Hill Zone will carry a wrecking ball when the highest bit of their subtype value is set. The object is fully functional, and can hurt Sonic. Technically, the swinging platforms of Marble Zone, Star Light Zone, and the swinging spikeball of Scrap Brain Zone are capable of doing this, too, but the wrecking ball graphics are not loaded, suggesting this feature was only intended for Green Hill Zone.

Warping effect

Warping.png

Thought to be the original method of accessing the special stage, this warp effect activates when Sonic touches the area in which the object is placed. Sonic disappears as he runs into it, and a warping noise plays. Sonic then reappears a few seconds later, likely as a method of testing the object.

Cheat device codes

These are cheat codes that can only be used with game enhancer devices. Support for these codes is available in most emulators.

Game Genie

Official codes

Code Effect Reference
ATBT-AA32 Master Code (Not needed in emulators).
AE3T-AACL You start with 1 life.
AY3T-AACL You start with 5 lives.
AE0T-CABE Once you gain Invincibility, you stay invincible until the stage ends, or when you die.
AE0T-CABY Once you gain Speed Shoes, you keep them until the stage ends, or when you die.
SCRA-BJX0 Each ring is worth 2.
SCRA-BNX0 Each ring is worth 3.
SCRA-BTX0 Each ring is worth 4.
SCRA-BYX0 Each ring is worth 5.
SCRA-B2X0 Each ring is worth 6.
SCRA-B6X0 Each ring is worth 7.
SCRA-BAX0 Each ring is worth 8.
SCRA-B9X0 Each ring is worth a crazy amount of rings.
GJ6A-CA7A Infinite lives.
AJ3A-AA4G Access to the Level Select menu.
AY3T-BA4R Start with 5 Chaos Emeralds in possession.
DDLT-AAGL Jump higher than your regular jump.
KDLT-AAGL Jump lower than your regular jump.
BDLT-AAGL Jump VERY high and "float" in the air.
NCLT-BYE6 Some Crabmeats go berserk.
NCLT-B9E6 Some Crabmeats disappear altogether.

Unofficial codes

Code Effect
663T-BA4R Max out score with one kill.
663T-B64R Start with 2 continues.
A23T-BA4R Start with all Chaos Emeralds.
AE2T-AAAL Enable Debug mode.
GLRT-AADY Ring count resets to 50 if Hit (Must have at least 1 ring).
NRRT-AADY Ring count resets to 99 if Hit (Must have at least 1 ring).
AA2A-ACC8 Start on Labyrinth Zone.
AA2A-AEC8 Start on Marble Zone.
AA2A-AGC8 Start on Star Light Zone.

Action Replay

Unofficial codes

Code Effect
00A35E:6042 Every Monitor Powerup gives Speed Shoes.
FFFE20:00C8 Infinite Rings (Turn off before passing end of level sign).
FFFE15:00FA Never run out of air Underwater.
FFFE2C:0001 Always have Shield.
FFFE24:0000 Infinite Time.
FFFE2D:0001 Invincibility (Monitor Effect without speed boost).
FFFFD0:0100 Enable Stage Select (A+Start on Title Screen).
FFFE10:XXYY Stage/Act Modifier (XX: Zone, YY: Level).
  • 00 - Green Hill Zone
  • 01 - Labyrinth Zone
  • 02 - Marble Zone
  • 03 - Star Light Zone
  • 04 - Spring Yard Zone
  • 05 - Scrap Brain Zone

Note: Scrap Brain Zone act 3 is accessed by using level code 03 for Labyrinth Zone (i.e. it is treated as the fourth act of Labyrinth Zone). Final Zone is considered to be the third act of Scrap Brain.

FFD861:0001 Final zone's first boss health equals 1.

User-Found codes

Code Effect
00D5CA:0005 Very Low Gravity
00CAA8:0532 Corrupted Spring Yard Title Card
FFF600:00YY Game Mode Modifier (YY: Mode).
  • 00 - SEGA Screen
  • 04 - Title Screen
  • 08 - Demo
  • 0C - Level
  • 10 - Special Stage
  • 14 - Continue Screen
  • 18 - Ending Scene
  • 1C - Credits
  • 8C - Pre-Level

References


Sonic the Hedgehog (16-bit)
Sonic1 title.png

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