Sonic the Hedgehog was the second of two Sonic games released for LeapFrog systems, following Sonic X, and like its predecessor contains educational aspects (in this case, spelling).
Unlike Sonic X, which was a reskin of another game, the Didj's Sonic couches the educational stuff in Genesis Sonic-style gameplay, bringing over numerous graphics, sounds, enemies, and items from those titles. One big difference is that the Special Stage rings take Sonic to the spelling challenges; the Chaos Emeralds (of which there are only three) are instead awarded for beating bosses, with the final boss giving up the Master Emerald. Unfortunately, the physics are far from perfect, resulting in some odd collision detection and making the final boss rather easy. (Oh, and Sonic has blue eyelids.)
Unused Sprites
Sonic
Sonic walking and running diagonally. In-game, his jumping/rolling sprites are used for diagonal movement instead.
While most of Sonic's sprites in this game are based on those from Sonic the Hedgehog 3, these are lifted from Sonic 2 despite equivalent sprites existing in Sonic 3.
Both walking animations have one frame where the sprites are dislodged from their intended maskings.
A version of Sonic's standing frame edited to make him look down. Amusingly, only his right eye was edited, making him look almost cross-eyed. One pixel of the mask is visible on the sprite.
Sonic hanging on a object, unused because there's nothing to hang on in this game. Notably, this also uses sprites from Sonic 2 despite equivalent Sonic 3 sprites existing.
Sonic celebrating. If this looks familiar, it's because it's part of the unused celebration animation from Sonic 1!
| To do: Confirm if this is really unused, as there are sections of water in the game. |
The drowning sprite from Sonic 3.
Debug Mode
A debug font that's used in Debug Mode.
Early HUD
A version of the HUD (taken from Sonic 1) without the line to track the number of Gadgets collected. It's possible the Gadgets idea (or at least the idea of tracking it in the HUD) came later in development.
Sonic's life counter icon without the text, suggesting that "SONIC" and the "×" symbol were separate sprites at one point. The final game stores it all as one sprite, likely for optimization.
| To do:
- Find code for these sprites if there's any.
- Find a way to implement these back into the game.
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Graphics/Sprites |
Notes
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A graphic of the Didj, probably intended for a controls screen.
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A graphic for a supposed rocket slider option that would've been in the Options menu.
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A slider handle for the above rocket slider.
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Unused light toggle sprites that would've let you enable...something.
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Unused A- and B-button sprites, could have been used for switching the jump button. Interestingly, the button shape here differs from those on the actual Didj (see above).
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A small arrow, likely for scrolling through more options.
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Unused Backgrounds
Emerald Hill Zone's background from Sonic 2, meant for the title screen (not the first time it was swapped out later in development). The title screen instead uses part of Emerald Hill Act 2 as the background.
Notably, a version of this background is used in the game's preview icon.
A blue background, purpose unknown. Could be a placeholder for the menu background.
Unused Objects
| To do: Check if there is any leftover unused code behaviors? |
A blank monitor. Similar to the used version, but with the top being a bit taller, to be used alongside...
...these numbers! It's possible the game was planned to feature math-related Special Stages in addition to spelling ones.
Here's what it looks like assembled.
Unused Icons
Unused |
Used |
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An unused version of the game's icon that's quite poorly resized and uses a brighter background.
Sprite |
Notes
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Green Hill Zone from Sonic 1.
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Chemical Plant Zone from Sonic 2.
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Scrap Brain Zone, also from Sonic 1. Oddly, the icon is a bit off-center.
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Hydrocity Zone from Sonic 3, also a bit off-center.
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Various icons for the Level Select.
Unused Audio
An alternate version of the sound used when Sonic loses rings.
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Sega Genesis | Sonic the Hedgehog (Prototype) • Sonic the Hedgehog 2 (Prototypes) • Sonic the Hedgehog 3 (Prototype) • Sonic & Knuckles (Prototypes) • Sonic 3 & Knuckles • Sonic 3D Blast (Prototypes) |
Sega Master System | Sonic the Hedgehog • Sonic the Hedgehog 2 • Sonic Chaos (Prototypes) • Sonic Blast |
Game Gear | Sonic the Hedgehog (Prototype) • Sonic the Hedgehog 2 (Prototype) • Sonic Chaos (Prototypes) • Sonic Triple Trouble (Prototypes) • Sonic Labyrinth • Sonic Blast (Prototypes) |
Arcade | SegaSonic the Hedgehog (Prototype) |
Sega CD | Sonic the Hedgehog CD (Prototypes) |
32X | Knuckles' Chaotix (Prototypes) |
Windows | Sonic the Hedgehog CD (1996) • Sonic 3D Blast • Sonic Heroes • Sonic Adventure DX: Director's Cut (2004) (Demo) • Sonic the Hedgehog 4: Episode I • Sonic the Hedgehog CD (2011) • Sonic Adventure DX: Director's Cut (2011) • Sonic Generations (Demos) • Sonic the Hedgehog 4: Episode II (Prototype) • Sonic Adventure 2 • Sonic Lost World • Sonic Mania • Sonic Forces • Sonic Colors: Ultimate • Sonic Frontiers • Sonic Superstars |
Sega Saturn | Sonic X-treme • Sonic 3D Blast (Prototype) |
Dreamcast | Sonic Adventure (Prototypes) • Sonic Adventure 2 (Prototypes) |
Neo Geo Pocket Color | Sonic the Hedgehog Pocket Adventure (Prototypes) |
GameCube | Sonic Adventure 2: Battle (Demo) • Sonic Adventure DX: Director's Cut (Prototypes) • Sonic Heroes (Prototypes) • Shadow the Hedgehog |
Game Boy Advance | Sonic Advance (Prototype) • Sonic Advance 2 (Prototype) • Sonic Advance 3 (Prototype) • Sonic the Hedgehog Genesis |
PlayStation 2 | Sonic Heroes (Prototype) • Shadow the Hedgehog • Sonic Unleashed |
Xbox | Sonic Heroes (Prototype) • Shadow the Hedgehog |
I-Mode, J2ME | Sonic the Hedgehog • Sonic the Hedgehog 2 |
N-Gage | Sonic N |
Nintendo DS | Sonic Rush (Demo) • Sonic Rush Adventure • Sonic Colors (Demo) |
Xbox 360 | Sonic the Hedgehog (Demo) • Sonic Unleashed (Preview) • Sonic Adventure DX: Director's Cut (Prototypes) • Sonic the Hedgehog 4: Episode I (Prototypes) • Sonic Generations (Demos) • Sonic the Hedgehog CD (2011) (Demo) • Sonic the Hedgehog 4: Episode II • Sonic Adventure 2 |
Wii | Sonic Unleashed • Sonic Colors • Sonic the Hedgehog 4: Episode I (Prototypes) • Sonic and the Secret Rings • Sonic and the Black Knight |
PlayStation 3 | Sonic the Hedgehog • Sonic Unleashed • Sonic Adventure DX: Director's Cut • Sonic the Hedgehog 4: Episode I • Sonic Generations (Demos) • Sonic the Hedgehog CD (2011) (Demo) • Sonic the Hedgehog 4: Episode II • Sonic Adventure 2 |
Nintendo 3DS | Sonic Generations • Sonic Lost World |
Wii U | Sonic Lost World |
PlayStation 4, Xbox One, Nintendo Switch | Sonic Mania • Sonic Forces • Sonic Colors: Ultimate • Sonic Frontiers • Sonic Superstars |
Amazon Luna | Sonic Mania • Sonic Colors: Ultimate |
PlayStation 5, Xbox Series X | Sonic Frontiers • Sonic Superstars |
iOS, Android, tvOS | Sonic the Hedgehog 4: Episode I (Prototypes) • Sonic the Hedgehog 4: Episode II (Prototype) • Sonic the Hedgehog • Sonic the Hedgehog 2 • Sonic the Hedgehog CD (Demo) |
Ouya, NVIDIA Shield | Sonic the Hedgehog 4: Episode I (Prototypes) • Sonic the Hedgehog 4: Episode II (Prototype) |
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Racing Games |
Game Gear | Sonic Drift • Sonic Drift 2 |
Windows | Sonic R • Sonic Riders • Sonic & SEGA All-Stars Racing • Sonic & All-Stars Racing Transformed • Team Sonic Racing |
Sega Saturn | Sonic R (Preview) |
PlayStation 2 | Sonic Riders (Prototype) • Sonic Riders: Zero Gravity |
PlayStation 3, Wii U | Sonic & All-Stars Racing Transformed |
GameCube, Xbox | Sonic Riders |
Nintendo DS | Sonic & SEGA All-Stars Racing |
PlayStation Portable | Sonic Rivals • Sonic Rivals 2 |
Xbox 360 | Sonic & SEGA All-Stars Racing • Sonic & All-Stars Racing Transformed • Sonic Free Riders |
Wii | Sonic & SEGA All-Stars Racing • Sonic Riders: Zero Gravity |
Nintendo 3DS | Sonic & All-Stars Racing Transformed |
PlayStation 4, Xbox One, Nintendo Switch, Amazon Luna | Team Sonic Racing |
Adobe Flash | Sonic Rivals Dash |
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Sports/Fighting Games |
Sega Genesis | Sonic the Hedgehog Spinball (Prototypes) |
Sega Master System | Sonic Spinball |
Game Gear | Sonic Spinball (Prototypes) |
Arcade | Sonic Championship • Mario & Sonic at the Rio 2016 Olympic Games |
Game Boy Advance | Sonic Battle |
Nintendo DS | Mario & Sonic at the Olympic Games • Mario & Sonic at the Olympic Winter Games |
Xbox 360 | Sonic the Fighters |
Wii | Mario & Sonic at the Olympic Games • Mario & Sonic at the Olympic Winter Games • Mario & Sonic at the London 2012 Olympic Games |
Nintendo 3DS | Mario & Sonic at the London 2012 Olympic Games |
Wii U | Mario & Sonic at the Rio 2016 Olympic Games |
J2ME | Sonic at the Olympic Games |
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Puzzle Games |
Sega Genesis | Sonic Eraser • Dr. Robotnik's Mean Bean Machine (Prototypes) |
Sega Master System, Game Gear | Dr. Robotnik's Mean Bean Machine |
Arcade | SegaSonic Bros. |
Adobe Flash | Sonic Jigsaw 2 |
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Educational |
Arcade | SegaSonic Cosmo Fighter |
Sega Master System | Sonic's Edusoft |
Windows | Sonic's Schoolhouse |
Sega Pico | Sonic the Hedgehog's Gameworld (Prototypes) • Tails and the Music Maker (Prototypes) |
Leapster | Sonic X |
LeapFrog Didj | Sonic the Hedgehog |
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Sonic Boom |
Wii U | Rise of Lyric (Prototype) |
Nintendo 3DS | Shattered Crystal • Fire & Ice |
Adobe Flash | Link 'n Smash |
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Compilations |
Sega Genesis | Sonic Classics |
Sega Saturn | Sonic Jam (Demo) |
Windows | Sonic & Knuckles Collection • Sonic Mega Collection Plus • Sonic Origins |
GameCube | Sonic Mega Collection (Prototype) • Sonic Gems Collection |
PlayStation 2 | Sonic Mega Collection Plus • Sonic Gems Collection |
Xbox | Sonic Mega Collection Plus |
Nintendo DS | Sonic Classic Collection |
Xbox One, Xbox Series X, PlayStation 4, PlayStation 5, Nintendo Switch | Sonic Origins |
Game.com | Sonic Jam |
Plug & Play | Super Sonic Gold |
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Other |
Game Gear | Tails' Skypatrol • Tails Adventures |
Sega Saturn | Sonic the Hedgehog into Dreams... |
Dreamcast | Sonic Shuffle (Debug Version) |
Nintendo DS | Sonic Chronicles: The Dark Brotherhood |
Windows, Mac OS X | The Murder of Sonic the Hedgehog |
I-Mode, J2ME | Sonic Jump |
iOS, Android | Sonic Jump • Sonic Dash • Sonic Runners • Sonic Runners Adventure (Prototype) |
Adobe Flash | Sonic The Broad Jump • Sonic and the Black Knight: Knight in Training |