Sonic & Knuckles (ソニック&ナックルズ Sonikku to Nakkuruzu?) is a 1994 platform video game in the Sonic the Hedgehog series for the Sega Genesis. It was developed in the United States at Sega Technical Institute by members of Sonic Team, and was published by Sega worldwide on October 18, 1994.In addition to being a standalone game, through a system dubbed "lock-on technology," Sonic & Knuckles acts as an expansion pack to both Sonic the Hedgehog 2 and Sonic the Hedgehog 3, the latter with which it was developed in tandem.

"Blue Sphere" redirects here. For the video game in the Star Ocean series, see Star Ocean: Blue Sphere.If the player uses the original Sonic the Hedgehog or Sonic Compilation, a screen with Sonic, Tails, Knuckles and Robotnik stating "No Way" repeatedly is displayed. By pressing the A, B and C buttons together, players can access a minigame based on the Special Stages of Sonic 3 and Sonic & Knuckles. Players can enter a twelve digit code on this screen, with every number combination generating a different variation of a Special Stage level. This game is retroactively known as Blue Sphere in Sonic Mega Collection.

Sonic the Hedgehog 3 and Sonic & Knuckles were originally to be released as one game,[4] but due to time and financial constraints, it was later split into two separate games. However, Sonic & Knuckles contained "Lock-on Technology", where the Sonic & Knuckles cartridge would be put in the Sega Genesis system, and then another game could be placed onto the top of the Sonic & Knuckles cartridge itself.[4] When Sonic 3 is used in this manner, it enables the player to play through both games as one, titled in-game as Sonic 3 & Knuckles. This features several additions to the games not available otherwise, such as small alterations to the levels, and being able to play through Sonic 3 levels as Knuckles, or Sonic & Knuckles levels as Tails, and the ability to save progress in all of the game's levels.Additionally, this was the only way to collect Super Emeralds, which are earned by accessing Special Stages in the Sonic & Knuckles levels after collecting all seven Chaos Emeralds from Sonic 3. When all Super Emeralds have been collected, Sonic, Knuckles and Tails can transform into Hyper Sonic, Hyper Knuckles and Super Tails respectively, each with unique abilities.

It's a Sonic the Hedgehog hack that includes Tails as a playable character, new/different layouts for every stage, different music ported from other Sega games, double boss fights in some zones and new moves!

Sonic the Hedgehog hack made by By Narcologer fully remade zones: Paradise Coast (GHZ), Border Fort (MZ), Dangerous Pit (LZ) and Robotropolis (SYZ) with new music, layouts, graphics and some new chunks. characters: Sonic, Mighty and Metal Sonic. Sonic can perform spin dash and peel out, Mighty can perform jump dash and double jump, Metal Sonic can only to spin dash but also he can't drown.Because 3 characters (and there will be more in future releases!) are too many for title screen I made a simple character select menu.A lot of new sprites.New Sega logo screen.And lots more!Credits:Programming: Narcologer, Vladikcomper, Sonic2010, EsraelNew level art, new chunks and layouts: NarcologerSprites: Narcologer, The Spriters Resource, SCAA, Lone DevilMusic: Ivan YO, STD, Nineko

Sonic Chaos Quest v2.0 is a modification of Sonic the Hedgehog. Story:Exploring Mobius seas Eggman found the Chaos Island. It has giant lake, on bottom of which the sunken ruins of Chaos Shrine which contain the inexhaustible power of Chaos are lying. In order to increase the power of his mechanisms Eggman built the Hydrostation on this lake and plans to conquer the world with the power which he got. Residents of the island asked Sonic for help, so he teamed up with Mighty, Tikal and Metal Sonic to start their Chaos Quest to stop Eggman's evil plans once again!Credits:Programming: Narcologer, Vladikcomper, TheBladNew level art: Narcologer, ShooterNew chunks and layouts: NarcologerSprites: Narcologer, The Spriters Resource, SCAA, Lone DevilMusic: Ivan YO, EgorTC, Nineko, TheBlad

Sonic Kyukyoku is a sonic the hedgehog hack made by Iso_KiloTeam Kyukyoku Credits: Iso Kilo, Gemini, G4, LJ Star, Mega Team, Foxivael, DashNK, Edgy The HedgySadly, there are too many outside sources to credit. But your contribution will not be forgotten. Music, art and code was borrowed, but by too many. If I named everyone, then it could fill an entire page in itself.Hope everyone enjoys the countless hours we put into this!

Mobius Evolution is a heavy modification of Sonic the Hedgehog for the Sega Mega Drive created by Abyssal Leopard with the help of fellow members. The aim of this hack was initially to be a simple level layout hack, but it eventually acquired new features, such as innovative gimmicks, boss battles and other things the player might discover in gameplay.