Sonic the Hedgehog 3

Sonic the Hedgehog 3 is the third game in the 16-bit Sonic trilogy and the first game with the redheaded echidna, Knuckles. Originally one big game, Sonic 3 was split into two games due to time constraints and cartridge costs; the second half of the story is its direct sequel, Sonic & Knuckles.

Level Select/Debug Mode


To access a level select and debug mode, press Up, Up, Down, Down, Up, Up, Up, Up after the SEGA logo screen fades to black, but before the title screen appears. The timing is fairly tricky; you'll hear the ring collection sound if you did it right. Alternatively, you can activate the Sonic 2 menu (see below) and enter the Sonic 2 level select code (19, 65, 09, 17).

To find the level select on the title screen, simply press Up to reveal "SOUND TEST" and press Start. To activate debug mode, select a file/level, hold A and press Start, and keep holding A until the level begins. You can also hold C and press Start to highlight high-priority background tiles (tiles that overlap Sonic and other sprites).

While in debug mode, you have access to the following:
 * Invincibility
 * Infinite time
 * Debug coordinates (in place of score)
 * Sprite counter (in place of time)
 * Placement mode: Press B to enter placement mode, which allows you to move Sonic anywhere in the level with the D-Pad and place objects from a predefined list (not all objects may be available in a given level). In this mode:
 * Press A to move forward one object.
 * Hold A and press C to move backward one object.
 * Press C to place the object.
 * Press B again to return to normal gameplay.
 * Character animation viewer: hold C and press B to rapidly cycle through all available animation frames for the current character (pause the game and use frame advance to view individual frames). Press B again to return to normal gameplay.
 * Pause options:
 * Press A to go back to the level select.
 * Hold B to progress the game in slow motion.
 * Press C to advance one frame.

If you die, press B to enter placement mode, and then press B at a safe spot to revive yourself. However, trying to place an object in this death state will freeze the game. Additionally, do not enter debug mode at any point where Sonic's sprite rotates (such as while standing on the red-and-white cylinders in Carnival Night Zone) or the game will crash.

Alternatively, use Game Genie code to access the level select.

A third way to unlock the level select menu (if you don't mind risking the long-term health of your console and cartridges) is to load up Sonic 2, unlock its level select (19, 65, 09, 17 in the sound test), swap the cartridge with Sonic 3 without turning the power off, and then press Reset. This works because the RAM variable that unlocks the level select is preserved when you reset the console (Sonic 3 was built upon the Sonic 2 source code, and thus shares a number of RAM variables).

Secrets
The level select menu shows what the level order was at one point. The Sonic 3 Zones are in their normal order, but Flying Battery from Sonic & Knuckles is listed between Carnival Night and Ice Cap. Following Launch Base are Mushroom Valley (an early name for Mushroom Hill) and Sandopolis, but neither of those can be selected.

According to commentary from the Sonic Jam strategy guide, Ice Cap was meant to follow Flying Battery as Sonic was supposed to break down the door at the end of the latter Zone and use it as a snowboard. It also mentions that Flying Battery was meant as the eighth zone, with Ice Cap being the ninth. There's also a variety of unused songs, all from Sonic & Knuckles, in the sound test.

Further, all the graphics here (including the level icons) are recycled from Sonic the Hedgehog 2, and the icons are shown in the Sonic 2 order, such as Emerald Hill's icon for Angel Island and Casino Night's icon for Carnival Night. Interestingly, the second "2P VS" entry shows the unused Hidden Palace icon from the Sonic 2 prototypes.

Red Revolving Spheres


A spinning mass of red spheres, which can be placed in the first half of Angel Island Act 1 via debug mode. The spheres resemble those that appear in the game's special stages, but the object itself seems to have no apparent gameplay purpose. When it is placed, many palette and VRAM complications occur in the level, and the game slows down considerably. The object can be manipulated with the second controller.


 * Up - rotates the object vertically.
 * Right - rotates the object horizontally.
 * Down/Left - moves the object up or down.
 * A/C - changes the object's size.
 * B - rotates the object sideways.
 * Start - toggles automatic rotation.

Knuckles Leftovers
Some data for Knuckles as a playable character seems to still exist in the game. Game Genie codes will allow you to "select" Knuckles as your character. You will play as Sonic, but have Knuckles' character select, continue icons, and "level-clearing" text. The end signpost will also feature Knuckles, though the image uses Sonic's blue palette. As you might expect, this code will save properly, allowing you to apply the code, create a save, then continue to use "Knuckles" even without the Game Genie.

8th Special Stage
There is an eighth Chaos Emerald (gray, much like the seventh Emerald) accessible via a hidden cheat code: go to the level select, set the sound test selection to 07, then hold A and press Start on the "Special Stage 2" selection.

This Emerald has no special effect in-game, however, and does not appear on the end-of-Special Stage tally in any form other than a score increase. Below is a map of this stage:



Flying Battery Zone
He4X19kUq90 As mentioned earlier, Flying Battery would have been played between Carnival Night and Ice Cap, but when the game was split into two that zone was moved into Sonic & Knuckles to give it more levels. Still, there's some leftovers in Sonic 3 – a data select icon, its music, and even its bosses!

While you can access Flying Battery by way of Pro Action Replay codes ( for Act 1, for Act 2), it will be corrupted with Ice Cap tiles appearing all over the place. However, you need to do this in a specific way because alone, these codes will crash the game when trying to access that level data.

While you can use codes to access other unused Zones (such as Lava Reef), those will crash the game.

Sonic 2 Options Menu
By setting the game's screen mode to, you can access the Sonic 2 options menu in Sonic 3! Alternatively, you can use the patch code or hack the menu back in yourself.

As all the options here are selectable normally through other means in Sonic 3, the only real benefit of this is entering the Sonic 2 level select code to access it in Sonic 3.

Unused Surfboard Intro
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Sprites for an alternate intro sequence in which Sonic surfs onto Angel Island, rather than riding in on the Tornado. Interestingly, Sonic looks like his Sonic 2 incarnation, making this a fairly old leftover. The surfing Sonic sprite can still be placed in Angel Island Zone 1 via debug mode.



The sprites used when Sonic ditches the surfboard.

Sonic


Sonic in his signature "waiting" pose, but instead of pointing towards the direction he's facing, he falls asleep from boredom instead. Interestingly, this animation was used for the Game.com version of Sonic Jam.



Sonic whistling, speculated to be part of a "help object" in early development. This was also used in the Game.com Sonic Jam.

Tails


A leftover animation from the Sonic 2 continue screen.

Knuckles


Unused gliding/climbing animations for Knuckles in 2-Player mode, despite him not having these abilities there.

Robotnik


A running frame where Robotnik has a different facial expression.



Appears to be nothing more than Eggman flying away towards the horizon.

Mini Death Egg


A smaller rendition of the Death Egg that seems to be part of a Death Egg hologram projector, which itself was unused in Sonic & Knuckles.

Diagonal Penguin Sprites


Diagonal frames of the penguin badnik from Ice Cap Zone. These can be seen for a split-second if you place a penguin on the large hill at the beginning of Act 1 using debug mode.

Flying Battery Data Select Icon


A save file icon for Flying Battery Zone before it was re-ordered to be in Sonic & Knuckles, which is different than the corresponding icon in Sonic 3 & Knuckles. You can view this icon in the PC and Genesis versions by hacking the save data to access level slot, or by using PAR codes to view it in a completed game save slot while scrolling through the levels.

Unused Music
Music from Sonic & Knuckles can be played from the level select/sound test.

The loop point in the "echo" track of the lead instrument is set slightly later than the rest of the tracks; as a result, it falls further and further out of sync every time the song loops. This was fixed in Sonic & Knuckles and its lock-on.
 * : Flying Battery Act 1


 * : Flying Battery Act 2
 * : Mushroom Valley/Hill Act 1
 * : Mushroom Valley/Hill Act 2
 * : Sandopolis Act 1
 * : Sandopolis Act 2
 * : Lava Reef Act 1
 * : Lava Reef Act 2/Hidden Palace
 * : Sky Sanctuary
 * : Death Egg Act 1
 * : Death Egg Act 2
 * : Sonic & Knuckles Act 1 Boss (can be heard while fighting any Hydrocity Zone boss if you jump out of the water after the drowning music starts)
 * : The Doomsday Zone
 * : Glowing Spheres Bonus Stage
 * : Slot Machine Bonus Stage

Scrolling Credits
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The game contains an unused, unfinished scrolling credits routine, which can be activated by setting RAM address to  during the credits sequence. The actual credits were apparently not yet in place when this was abandoned, as it scrolls small and large versions of the letters B-F, and then abruptly fades to the Sonic 3 logo screen. The final staff roll simply fades between static pages of text.

Miscellaneous
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 * Like Sonic 2, all versions of Sonic 3 have both English and Japanese content. However, lockout prevents Sonic 3 US or PAL versions from seeing the "Miles" level end card, or Japan versions from seeing the "Tails" level end card. Using a region patch code will restore this behavior.
 * Due to a glitch, if one stays on the save screen for around 47 minutes, one of the instruments in the song will increase in volume...for some reason. The bug was fixed in Sonic 3 & Knuckles.
 * Knuckles' theme is just a set of drums that lasts for roughly two seconds, and loops forever. However, at around the 34-second mark (@60FPS) is a brief voice sample before the next section of drums. This in and of itself isn't particularly interesting, but it should also be noted that whenever the song plays in-game it's always in scripted events; the song only ever plays for a maximum of 10 seconds or so. The only way to listen to this small sample is to use the sound test.