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

Back to: Sonic the Hedgehog 2 (8-bit).

Zone select

In the Master System version, hold + + 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 or on Controller 1.

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

Extra acceleration

Pressing and 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

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

	This list is incomplete. The following list has been marked as incomplete. If you can, please complete it.

Art

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.
	The entire body of Pit Master can be seen here. Normally, only its head is visible.
	The entire body of Hiyoko Master 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. Shown in footage from Sega Shinsaku Soft Video Vol. 23, however it did nothing when broken.
	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.
	Under Ground Zone Bricks. These were originally used for the Zone in the AutoDemo prototype.
	The remains of Green Hill Zone-style tubes for Under Ground Zone from the AutoDemo prototype.
	Miscellaneous Under Ground Zone tiles.
	Under Ground Zone floating platform.
	Sky High Zone boulder intended to roll down a hill in Act 1. Shown in footage from Sega Shinsaku Soft Video Vol. 23.
	Sky High Zone platform.
	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

Music

Audio	ID	Description
	`92`	A peaceful, ethereal-sounding tune of unknown purpose that is unused in the Master System version. 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.

Sound effects

Audio	ID	Description
	`A7`	Similar to the sound used for Springs and ramps in the AutoDemo.
	`AC`	Sounds like a fire sound.
	`AD`	An alternate splash sound.
	`B2`	Similar to sound A2 in the AutoDemo.

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:

v1.0	MS SONIC¥THE¥HEDGEHOG.2 Ver1.00 1992/09/05 SEGA /Aspect Co.,Ltd
v2.2	MS SONIC¥THE¥HEDGEHOG.2 Ver2.20 1992/12/09 SEGA /Aspect Co.,Ltd
	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.