Sonic the Hedgehog 2 (8-bit)/Hidden content

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Level select


In the Master System version, hold Left + 1 + 2 on Controller 2 when powering on the game, and keep them held down during the opening sequence. When the title screen appears, release the buttons, then press 1 or 2 on Controller 1.

In the Game Gear version, hold DownLeft + 1 + 2 during the SEGA screen and keep them held down. Then, you can press Start to skip the intro. Finally, on the title screen, press Start again when Tails blinks exactly for the third time (while still maintaining the other buttons).

Extra acceleration

Pressing Left and Right at the same time on the D-Pad will result in incredible acceleration and speed to the left. This is mainly useful in emulation (and has been extensively used in a Tool-Assisted Speedrun[1]), while it's unfeasible on a real unmodified console.

Hidden birds in Sky High Zone

Sonic2 SMS HiddenBirds.png

If the player locates the 1UP Monitor at the top left of Sky High Zone Act 1 and walks into the left side of the Monitor without breaking it, yellow birds will come out of the trees. The player can make more birds come out after the birds have gone off-screen by walking into the Monitor again. This can happen in both Master System and Game Gear versions.

Unused content


Art Description
Some unused sprites of Tails crying. Probably meant to be used in the ending cutscene when he is rescued.
This animation is from Sonic 1 for the Master System, but were found in Sonic 2 for the Game Gear. While Sonic originally had this animation in the AutoDemo, it was changed for the final release.
Sonic's death sprite from the Master System version of Sonic 1. The final version uses an updated sprite.
UZ Boss.png
The entire body of Arijigoku Mecha can be seen here. Normally, only its head is visible.
The entire body of Gachou Mecha was also drawn. Normally, only its head and neck can be seen.
Sonic monitor. This one isn't really unused; the player can find it hidden in a wall in Crystal Egg Zone, but the graphics are obscured. When collected, it grants a Continue.
Question mark monitor, possibly set to give the player a random amount of Rings or items, like in the 2-player mode of Sonic 2 for the Mega Drive.
Grey Sneaker monitor which might have slowed down the player, similar to the Slow sneaker in Sonic 3's Competition mode.
This could have been a checkpoint marker, like in the 8-bit version of Sonic 1.
UZ bricks.png
Under Ground Zone Bricks. These were originally used for the Zone in the AutoDemo prototype.
UZ loop.png
The remains of Green Hill Zone-style tubes for Under Ground Zone from the AutoDemo prototype.
Miscellaneous Under Ground Zone tiles.
UZ platform.PNG
Under Ground Zone floating platform.
Sky High Zone boulder, probably meant to roll down a hill in Act 1.
S2 8bit skyhigh platform.png
Sky High Zone platform.
S2 8bit skyhigh block.png
Sky High Zone object - probably another platform.
Unused Aqua Lake Zone water slide. These are fully functional if placed in Act 2, causing Sonic to slide down them like in Labyrinth Zone.


Audio Description
In the Master System version, song ID $92 is occupied by a peaceful, ethereal-sounding tune of unknown purpose that is unused. In the Game Gear version, this song was replaced with the sound effect that plays when Sonic (and Tails) looks up at the stars at the end of the credits.

Gimmick Mountain name


Originally the level card for Gimmick Mt. Zone wasn't going to have a shortened name. Hivebrain discovered the word "Mountain" within the ROM. Due to lack of space on the screen Mountain was shortened to Mt.

Build date

Similar to other games developed by Aspect, the game's build date can be located at ROM address $C0:

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

Cheat device codes

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

Game Genie

Official codes, Game Gear version

Code Effect Reference
009-04F-3BE Infinite lives.
012-B8D-E66 Start with 1 life.
052-B8D-E66 Start with 5 lives.
092-B8D-E66 Start with 9 lives.
A78-92C-19E Invincible after 1 ring (Except on act 3).
026-5ED-E6E Each ring worth 2.
036-5ED-E6E Each ring worth 3.
046-5ED-E6E Each ring worth 4.
056-5ED-E6E Each ring worth 5.
066-5ED-E6E Each ring worth 6.
076-5ED-E6E Each ring worth 7.
086-5ED-E6E Each ring worth 8.
3A7-E4C-2A2 Don't lose rings when hit.
001-12D-3B7 Stop timer.
3E2-E4D-3B4 + 012-E5D-E69 Start on Act 2.
3E2-E4D-3B4 + 022-E5D-E69 Start on Act 3.

Pro Action Replay

Unofficial codes, Game Gear and Master System version 1.0 and 2.2

Code Effect
00D3A9:15 Become Invincible After Being Hit.
00D298:09 Infinite Lives.
00D299:63 Infinite Rings (Press button 1 at end of level during score totaling).
00D2BA:00 Keeps Time At Zero (Minutes).
00D2B9:00 Keeps Time At Zero (Seconds).
00D295:0? Zone Select (Enable switch after the first 2 screens but before the level starts, after the level starts disable).
  • 0: Underground
  • 1: Sky High
  • 2: Aqua Lake
  • 3: Green Hills
  • 4: Gimmick Mountain
  • 5: Scrambled Egg
  • 6: Crystal Egg
00D296:0? Act Select (Enable switch after the first 2 screens but before the level starts, after the level starts disable).
  • 0: Act 1
  • 1: Act 2
  • 2: Act 3
00D502:13 Start with Glider.


Sonic the Hedgehog 2 (8-bit)
S2 sms title.png

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