Sonic the Hedgehog

Sonic the Hedgehog is a media franchise created and produced by Sega. It is primarily a video game franchise, centering on a series of speed-based platform games. Sonic, the protagonist, is an anthropomorphic blue hedgehog with supersonic speed, capable of reaching the speed of sound. Typically, Sonic—usually along with some of his friends, such as Tails, Amy, and Knuckles—must stop antagonist Doctor Eggman's plans for world domination.

The first game in the series, released in 1991, was conceived by Sega's Sonic Team division after Sega requested a mascot character. Its success spawned many sequels and helped Sega become one of the leading video game companies during the 16-bit era of the early 1990s.

While the first Sonic games were side-scrolling platform games, later games expanded into other genres, such as Mario & Sonic at the Olympic Games. The series and its spin-offs had sold over 80million physical copies by June 2011, and grossed over US$5 billion by 2014. As of 2018, the series has shifted 800million units, including free-to-play mobile game downloads. The franchise has also been spun out into other media, including cartoons, anime, and a comic book series recognized as the longest running based on a video game by Guinness World Records.

Sega Genesis (1991–1996)
The first Sonic game, Sonic the Hedgehog, is a platform game released in 1991. Players control the anthropomorphic blue hedgehog Sonic, who can run and jump at high speeds using springs, ramps, and loops. Sonic must stop Dr. Robotnik from taking over the world using the Chaos Emeralds. Sonic the Hedgehog 2 (1992) increased the overall size and speed of the series' gameplay and was the second best-selling Genesis game. It introduced Sonic's sidekick and best friend, Miles "Tails" Prower, who followed Sonic throughout the game, and allowed a second player to control him in a limited fashion. This game also introduced Sonic's "spin dash" maneuver, an ability which allows Sonic to burst forwards quickly from a complete standstill, unlike the previous game, where Sonic could only gain speed with momentum. Sonic 2 was followed in 1993 by an arcade game, SegaSonic the Hedgehog, featuring new characters Mighty the Armadillo and Ray the Flying Squirrel.

The next console game, Sonic the Hedgehog 3, was released in 1994. The game introduced a temporary shield maneuver, often called the "insta-shield", added new shield types to the series, and allowed Tails to be completely playable under a second player's control, as well as adding the option for players to utilize Tails' flying ability in levels. It also introduced the character, Knuckles the Echidna, who served as an additional antagonist with Doctor Robotnik for the game.

Sonic & Knuckles, another platform game in the Sonic series, was released later in 1994. The game featured Knuckles as a playable character with gliding and wall climbing abilities and allowed gamers to plug in Sonic the Hedgehog 3 to the top of the Sonic and Knuckles cartridge as part of the game's "lock on" functionality. This allowed gamers to play the game as it was originally intended; the games were intended to be one game, but were split due to cartridge space and time constraints.

There were several Sonic games for the Genesis that were not 2D platform games. Sonic Spinball, released in 1993, was a pinball simulation modeled after the Spring Yard and Casino Night Zones from the first two Sonic games. The game, unlike general pinball simulations, had an overall goal of collecting all the Chaos Emeralds in each level and defeating the levels' bosses. It was one of the few video games that had elements from the cartoons Sonic the Hedgehog and Adventures of Sonic the Hedgehog. Dr. Robotnik's Mean Bean Machine was a puzzle game similar to Puyo Puyo that was set in the Adventures of Sonic the Hedgehog universe. Sonic 3D Blast, an isometric, 2.5D platform game released in 1996 and developed by Traveller's Tales, featured Sonic running through pseudo-3D environments while trying to rescue Flickies from Doctor Robotnik.

The Sega Genesis had "add-on" systems that incorporated Sonic games. Sonic CD, released for the Sega CD, was a 2D platform game released in 1993. The game introduced the characters Amy Rose and Metal Sonic and featured levels that differed depending upon whether Sonic was in the past, present, or future time frames. Knuckles' Chaotix, a spin-off released in 1995 for the Sega 32X, featured Knuckles and a new group named Chaotix fighting against Dr. Robotnik. The game featured a two-player cooperative system in which the on-screen characters were connected by magic rings. There was also Sonic Eraser, a puzzle game released exclusively on Sega Game Toshokan in 1991.

Due to the success of Sonic games on the Sega Genesis, the series was introduced to the Sega Master System and Sega Game Gear. Sega began by releasing Sonic the Hedgehog, a 2D platform game, in 1991. The game featured Sonic's ability to run and to jump at high speeds like its Mega Drive/Genesis counterpart but with notably different level design and music. Sega later released Sonic the Hedgehog 2 another 2D platform game, in 1992. The game differed from its Genesis counterpart with different levels and music and by not including a "spin dash" maneuver. It also featured a different storyline in which Doctor Robotnik kidnaps Tails, who is non-playable in the Master System/Game Gear version. Sonic Chaos/Sonic and Tails (Japan), released in 1993, was similar to the earlier two Sega Master System/Game Gear Sonic games, but featured Tails as a playable character. A sequel, Sonic Triple Trouble/Sonic and Tails 2 (Japan), a 2D platform game, was released in 1994 for the Game Gear and introduced a new character, Nack the Weasel, who, along with Knuckles and Doctor Robotnik, raced to collect the Chaos Emeralds. One of the last games for the Sega Game Gear, Sonic Blast, was released in 1996 and featured prerendered sprites.

Several spin-off Sonic games that were not 2D platform games were also released. Sonic Labyrinth, released for Game Gear in 1995, featured an isometric view and slower exploration-based gameplay that resulted from Robotnik's replacing Sonic's shoes with "Speed Down Boots." Sonic Drift was a kart racer released in 1994. It later had a sequel, Sonic Drift 2, which was released in 1995. Tails also received two spin-offs. Tails' Skypatrol, released in 1995, allowed players to control an always-flying Tails. Tails Adventure, released in 1995, featured a mix of platforming and RPG elements.

Sega Saturn (1996–1998)
Few Sonic games were released for the Sega Saturn, and none were a standard platform game originally made for the system. Sonic 3D Blast was released in 1996 alongside the Genesis version. Like its Genesis counterpart, the Saturn edition used isometric, 2.5D graphics, but it added FMV cut-scenes, enhanced music and visual effects, and a real-time 3D special stage. Sonic Jam, a compilation released for the Saturn in 1997, contained the original Sonic the Hedgehog, Sonic the Hedgehog 2, Sonic the Hedgehog 3, and Sonic & Knuckles, as well as a "Sonic World" mode, which allowed the player to control Sonic in a small 3D world. The Sonic World was mainly a means of accessing the disc's multimedia features, which included character artwork, the soundtrack, and Japanese Sonic videos. Sonic R, a foot racing spin-off and also the Sonic series' first fully 3D game, was released in 1997 for the Saturn and ported to the PC in 1998.

The Sega Technical Institute attempted to develop a Sonic game for the Saturn called Sonic X-treme. It was originally intended to compete with Nintendo's Super Mario 64 and Sony's Crash Bandicoot. However, due to time constraints and issues between STI, the Japanese division of Sega, and Sonic Team, the project was canceled in late 1996.

Dreamcast (1998–2001)
Sonic Adventure, a launch game for the Dreamcast, was released in 1998 in Japan and 1999 in North America. The game was re-released for the GameCube and PC as Sonic Adventure DX: Director's Cut in 2003 with some graphical and gameplay tweaks, and, in late 2010, ported to Xbox Live Arcade and PlayStation Network. Its sequel, Sonic Adventure 2, was released for the Dreamcast in 2001, and was the last game in the series to be released for the Sega platform. In 2002 it became the first game in the series to appear on a Nintendo platform when it was ported – with several enhancements – to the GameCube as Sonic Adventure 2: Battle, and in October 2012 it was ported to Xbox Live Arcade and PlayStation Network with a version released on Steam in November the same year.

The only other Dreamcast Sonic game was Sonic Shuffle, which was released in 2000 and featured cel-shaded graphics and a board game concept similar to that of the Mario Party series. Dreamcast sales began to decline after the launch of the PlayStation 2, and therefore few Sonic games were released for the system.

Sonic the Hedgehog Pocket Adventure was also released on SNK's Neo Geo Pocket Color portable console, made in the same style of the Genesis/Mega Drive era of games.

Move to non-Sega systems (2001–2006)
After the commercial failure of the Dreamcast, Sega ceased producing its own video game hardware, focusing solely on manufacturing software for the GameCube, followed by releases for the PlayStation 2 and Xbox.

Sonic's transition to the Game Boy Advance was completed with Sonic Advance, the first original Sonic game released for a Nintendo console. The game featured 2D platforming, similar to the original Genesis games, and new gameplay mechanics from more recent Sonic games as well, such as grinding on rails. It was released in late 2001 in Japan and early 2002 elsewhere, and ported to Nokia's N-Gage on October 7, 2003, as SonicN. Two sequels, Sonic Advance 2 and Sonic Advance 3, followed in March 2003 and June 2004, respectively.

Between Sonic Advance 2 and Sonic Advance 3, two other Sonic games were released: Sonic Battle, a 3D fighting game, and Sonic Pinball Party, a pinball simulation. The last Sonic game was released for the Game Boy Advance is Sonic The Hedgehog Genesis on 2006, which features the original Genesis game and the 15-anniversary mode with the Spin Dash.

The first game released for the GameCube was Sonic Adventure 2: Battle, followed by Sonic Adventure DX: Director's Cut, each ports from the Dreamcast. Sega later released Sonic Heroes, the first Sonic game made for the GameCube, PlayStation 2, and Xbox. It was released on all three systems on December 30, 2003 in Japan, with American and European releases following soon after. The game was similar to that of the Adventure games, although the player now controlled the lead character of a team of three, with the other two following behind. The player could then switch to a new leader at any time in order to use that character's special abilities.

Shadow the Hedgehog was released in late 2005 in North America. It was built on a more advanced version of the engine used for Sonic Heroes. It focused on Shadow the Hedgehog as he tried to uncover his past. The game contained multiple paths and endings, as the player chose to take good or evil paths for each level. It also added wielding weapons and driving vehicles to 3D platforming.

Sonic Riders was the first Sonic racing game since Sonic R; in contrast to the previous game, the characters used hoverboards, bikes, and skates rather than racing on foot. It was the last game for GameCube & Xbox.

Due to the extended life cycle of the PlayStation 2, it also received ports of Sonic Riders: Zero Gravity and Sonic Unleashed. Two Sonic games appeared on the PlayStation Portable: Sonic Rivals and its sequel, Sonic Rivals 2. Both games were 2.5D style games.

Seventh generation consoles (2006–2013)
There were a number of different Sonic games released for the Nintendo DS. The first was Sonic Rush, released in 2005, featuring gameplay similar to the Sonic Advance series. It received a sequel, Sonic Rush Adventure, in 2007, which featured some additional new elements, such as the driving of jet skis and submarines. Along with the Wii, the Nintendo DS saw the beginning of the Mario and Sonic crossover games. The first, Mario & Sonic at the Olympic Games, was released in late 2007, and featured characters from both series competing in Olympic-themed mini-games. Its sequel, Mario & Sonic at the Olympic Winter Games, was released in October 2009, and featured an emphasis on winter-based sports. Sonic Chronicles: The Dark Brotherhood, a spin-off released in September 2008, was a turn-based role playing game developed by BioWare.

During this timeframe, Sega took the franchise in a number of different directions. First was Sonic the Hedgehog, which was released in November 2006 for the Xbox 360 and December 2006 for the PlayStation 3. It continued in the Sonic Adventure direction, but was critically panned as a result of its glitches and rushed release. Sonic Unleashed was released in 2008 for the Xbox 360, Wii, PlayStation 2 and PlayStation 3. While possessing the same name and rough themes, the Xbox 360 and PlayStation 3 versions were markedly different games from the Wii and PlayStation 2 versions.

While the prior game in the era continued the use of numerous playable characters and play styles, the following games would return to only have Sonic playable. Sonic the Hedgehog 4: Episode I, an episodic high-definition 2D game akin to the 16-bit Sonic games, was developed for the PlayStation Network, Xbox Live Arcade, WiiWare. Sonic the Hedgehog 4: Episode II was released in 2012 for PlayStation Network, Xbox Live, Android, iOS, and Windows Phones. Sonic Colors, a game for the Wii and Nintendo DS, was released in November 2010. It introduced a power-up system in the form of alien beings called "Wisps". Sonic Generations was developed by Sonic Team for Xbox 360, PlayStation 3, PC and Dimps for Nintendo 3DS which was released in November 2011, featuring both modern and classic interpretations of Sonic.

During this time, the franchise also moved into several new spin-off series. The Storybook series, which combines Sonic gameplay with the story and setting of famous books, comprises two games only released for the Wii: Sonic and the Secret Rings (released in 2007) and Sonic and the Black Knight (released in 2009).

Another spin-off series resulted from Sega's collaboration with Nintendo and their Mario series of video games. In the Mario & Sonic games, characters from the Sonic and Mario universes compete in Olympic Games-themed minigames. Separately from that series, Sega also collaborated with Nintendo to include Sonic in their 2008 Wii fighting game Super Smash Bros. Brawl.

Sonic Colors, released in November 2010, expanded further on the Rush series gameplay with the addition of the use of "Wisps", which gave Sonic various new power-ups and gimmicks. Sonic Free Riders was released in November 2010 as a follow-up to the Sonic Riders series, and was developed exclusively for Xbox 360's Kinect system. Later on, Sega Superstars Tennis for the Wii, Xbox 360, PlayStation 3, PlayStation 2 and Nintendo DS was released in 2008 and Sonic & Sega All-Stars Racing for the Wii, Xbox 360, PlayStation 3, Nintendo DS and PC and iOS was released in 2010, followed by a sequel in 2012.

Even early in the system's life cycle, a number of Sonic games were announced for the Nintendo 3DS. At E3 2010, an untitled Sonic game was announced for the system, which later turned out to be a portable version of Sonic Generations. A third installment of the Mario & Sonic crossover series, Mario & Sonic at the London 2012 Olympic Games was also released for the Nintendo 3DS. Sonic & All-Stars Racing Transformed was released for the Nintendo 3DS in February 2013, and for the PlayStation Vita in November 2012. In October 2012, Sonic Jump was released on iOS, and in March 2013, Sonic Dash was released.

Eighth-generation consoles (2013–present)
In May 2013, Sega announced a partnership with Nintendo, which established that the next three Sonic games would be developed exclusively for the Nintendo 3DS and Wii U, with Nintendo publishing the games in Europe and Australia. The first games to be released was Sonic Lost World in 2013, followed by Mario & Sonic at the Sochi 2014 Olympic Winter Games by the end of the year. Sonic Boom: Rise of Lyric for the Wii U, and Sonic Boom: Shattered Crystal for the Nintendo 3DS, based on the new Sonic Boom franchise, together formed the final installment(s) in the exclusivity agreement. At the end of 2014, Sonic also returned as a fighter in both installments of Super Smash Bros. for Nintendo 3DS and Wii U. Sonic was added as a playable character in the Lego video game, Lego Dimensions, in November 2016; he is distributed via a "Level Pack" that includes an additional Sonic the Hedgehog-themed level and vehicles.

Two Sonic games were revealed at the Sonic 25th Anniversary Event during San Diego Comic-Con 2016. The first game was Sonic Mania, which emulates the gameplay and visuals of the original Sega Genesis games, and was released in August 2017 to critical acclaim, with critics hailing it as a return to form for Sonic. Development was done by PagodaWest Games, Christian Whitehead, and Headcannon's Simon Thomley. The second game, Sonic Forces, was developed by Sonic Team and released in November 2017. Sonic Forces brings back the dual gameplay of Sonic Generations, along with a third gameplay style featuring the "Avatar", a customizable third character who uses special gadgets called Wispons. Both games were released for the PlayStation 4, Xbox One, Nintendo Switch, and Microsoft Windows.

Characters
The Sonic series has a great many characters; the most frequently appearing are titular protagonist Sonic the Hedgehog, a blue hedgehog able to run at supersonic speeds, and recurring villain Dr. Eggman, an evil scientist whose ambition is to conquer the world. Among Sonic's many allies, the most well-known include: Miles "Tails" Prower, a twin-tailed, highly intelligent yellow fox who is Sonic's sidekick and best friend; Amy Rose, a pink hedgehog who is Sonic's self-proclaimed girlfriend and a hero in her own right; Knuckles the Echidna, a coolheaded red echidna who is the guardian of the Master Emerald; Shadow the Hedgehog, an anti-heroic doppelgänger of Sonic with a dark past; and Metal Sonic, a robotic clone of Sonic, built by Doctor Eggman with a sole purpose of destroying Sonic.

Rings
One distinctive feature of Sonic games are collectible golden rings spread throughout the levels. This gameplay device allows players possessing at least one ring to survive upon sustaining damage from an enemy or hazardous object; instead of dying, the player's rings are scattered. In most Sonic games, a hit causes the player to lose all of the rings, although in certain games a hit only costs a set number of rings such as ten or twenty. When the rings are scattered, the player has a short amount of time to re-collect some of them before they disappear.

Some causes of death cannot be prevented by holding a ring, including being crushed, falling into a bottomless pit, drowning, and running out of time.

In many games, collecting 100 rings usually rewards Sonic or any other playable character an extra life. Certain games in the series often reward the collection of 50 rings with Chaos Emeralds, access to the Special Stages in which the Chaos Emeralds may be obtained, or utilization of a character's super transformation.

Rings have had other uses in various games as well, such as currency (Sonic Adventure 2), restoring health bars (Sonic Unleashed), or improving statistics (Sonic Riders).

Chaos Emeralds
The Chaos Emeralds are, in most games, seven emeralds with mystical powers; they are a recurring feature of Sonic games. The emeralds can turn thoughts into power, warp time and space with a technique called Chaos Control, give energy to all living things and be used to create nuclear or laser based weaponry.

They are the basis of many of the games' plots, and the player is frequently required to collect them all to fully defeat Doctor Eggman and achieve the games' good endings, super forms, or both. The methods used to acquire the Emeralds and the end-results after collecting them differ between games in the series. Most early games require the player to find the emeralds in Special Stages, while some modern games implement the emeralds as a plot element. In certain games, such as Sonic R and the 8-bit versions of Sonic the Hedgehog and Sonic the Hedgehog 2, the player is required to find the Chaos Emeralds within the zones themselves.

The Master Emerald was introduced in Sonic & Knuckles as a plot element. It resides in a shrine on Angel Island and is guarded by Knuckles the Echidna, as only those of the Echidna Tribe are able to control it. The power of the Master Emerald is what keeps Angel Island afloat in the sky. It can control the power of the Chaos Emeralds, including neutralizing or amplifying their energies. In both Sonic Adventure and Sonic Adventure 2, the Master Emerald becomes shattered, requiring Knuckles to find the scattered pieces during his levels.

Special Stages
Usually, Special Stages were employed as a means of earning Chaos Emeralds. Special Stages usually take place in surreal environments and feature alternate gameplay mechanics to the standard platforming of the main levels. The 16-bit Sonic the Hedgehog  consisted of a giant rotating maze, which many considered a major technical achievement. The most common special stages, however, were segments with the character running through a long tunnel to collect certain items. 3D "collect item" levels, as in Sonic 3 and Sonic & Knuckles, used the same perspective but had Sonic collecting all the blue-colored orbs on the surface of a giant sphere. Finally, Sonic Advance 2 employed a 3D ring-collecting stage, and Sonic Chaos (Sonic and Tails in Japan) used a variety of gimmicks for its levels. Since Emeralds of the 8-bit version of Sonic the Hedgehog were hidden in the main stages, the game's spring-filled Special Stages were merely used as a means of adding variety, increasing score and earning continues. Similarly, Sonic 3 & Knuckles, in addition to the main Special Stages, featured entirely optional bonus stages, one of which combined the rotating maze of Sonic the Hedgehog with the pinball gambling of Sonic the Hedgehog 2. Sonic Heroes contained an alternate Special Stage for a chance of earning additional lives.

Super transformation
A super transformation is a state certain characters go into that gives them incredible speed, near-invincibility and a change in color. In some games, characters are still vulnerable to being crushed, drowning, falling into a pit or running out of time. Depending on the type of transformation, the condition to attain such a form is an individual making contact with all of the Chaos Emeralds, the Sol Emeralds, or the Master Emerald.

Super transformations first appeared in Sonic the Hedgehog 2, where Sonic transforms into Super Sonic if all seven Chaos Emeralds and fifty or more rings are held at the same time. While in Super Sonic form, Sonic gains invincibility (except from instant-kill obstacles) and has greatly increased speed. One ring is lost for every second that passes, and Sonic reverts to normal if the number of rings drops to zero. In Sonic 3 & Knuckles, Tails can also transform after gaining all seven Chaos Emeralds and Super Emeralds. Sonic and Knuckles can also transform into their hyper counterparts with the Super Emeralds. Hyper Sonic, Hyper Knuckles, and Super Tails all have unique abilities aside from invincibility and increased speed.

In most 3D Sonic games starting with Sonic Adventure, Chaos Emeralds are collected in non-interactive cut scenes as part of the story, with Super Sonic and other super characters only appearing in the final boss fights. Most 2D Sonic platform games, like the Advance and Rush series, have retained the gameplay-based emerald collecting, but still have Super Sonic only playable in the "Extra" boss battles. Recent games such as Sonic the Hedgehog 4, Sonic Colors, Sonic Generations, and Sonic Lost World once again allow players to play as Super Sonic during normal stages, provided they have all the Chaos Emeralds.

Sonic, Tails, Knuckles, Metal Sonic, Shadow, Blaze, and Silver are the characters that are known to be able to perform super transformations. Metal Sonic can also use the Master Emerald or Chaos Emeralds to turn Super, and Blaze, instead of using the Chaos Emeralds, uses the Sol Emeralds (her dimension's equivalent).

Along with Sonic, Mega Man (fused with the Rush Adaptor) achieved the Super transformation in the Archie Comics crossover Worlds Collide so that the two could restore the damage to their worlds done by Doctor Eggman and Dr. Wily.

Item boxes
These are containers that hold power-ups and appear frequently throughout the stages. An icon on each box indicates what it contains, and the player releases the item by destroying the box. In the early games, item boxes resembled television sets and could only be destroyed with an attack; in later games, they became transparent capsule-like objects easily destroyed with one touch. Common items in boxes include rings, a barrier (or shield), invincibility, high speed (or power sneakers) and 1-ups.

The barrier is a spherical energy shield which surrounds and protects the player's character from one attack; when hit, the barrier is lost instead of rings or a life. In Sonic 3, additional barriers were introduced which gave the player special abilities, such as the ability to magnetically attract rings and double jump, breathe underwater, or resist fire.

Invincibility temporarily protects against damage done by enemies and obstacles, and allows the player to destroy enemies by touching them and not lose any rings. Death from crushing, falling, drowning and time-ups, however, are still possible.

High speed boxes give the player character enhanced speed for a limited time.

1-up boxes display the face of the player's character and give the player one extra life. In the event that a player loses a stage, this enables the player to restart the level at the starting point, or, if one has been passed, close to the last checkpoint. Multiple lives can be collected, generally up to 99.

Other item boxes featured include a box with Robotnik's face on it, which cause damage to whoever opens it, a "teleport box" (Sonic 2's 2-player mode only), which swapped both players' positions, and a skateboard box (Sonic Generations only), which allows the player to ride a skateboard for a short time.

Giant Rings
Giant rings (Warp Rings) were featured in a few Sonic games, mainly from the 16-bit era. Rather than collecting them, as is the case with the smaller ones, they served as a portal to enter a Special Stage, where the player could collect one of the Chaos Emeralds. In Sonic the Hedgehog 3, if all Emeralds have already been found, touching them rewards the player fifty rings. In most games since Sonic Adventure 2, these giant rings serve as the end level marker, which ends the level upon touching it.

Checkpoints
Checkpoints are items placed throughout the stages in Sonic games which serve mainly as progress markers. If the player runs through one, their progress through a level is "saved". If the player then loses a life on the same stage, they will start over at the last checkpoint passed. Checkpoints also serve other uses in various games, such as entering Special Stages in Sonic the Hedgehog 2, and leveling up in Sonic Heroes. In the 2D games, checkpoints take the appearance of posts, while in 3D games they are either small gates or pads on the ground.

Springs
Springs are a staple in the Sonic series. They are scattered throughout the levels and serve to catapult the player at high speeds in a particular direction. Sometimes they allow the player to proceed further in the level, while other times they are used to hinder the player, usually by sending Sonic towards a dangerous area. Sonic Unleashed in particular features springs with Dr. Eggman's face on them that launch Sonic towards danger or hinder his progress. Springs serve as one of Sonic's special moves in Super Smash Bros. Brawl.

Animals
In addition to anthropomorphic animals, the Sonic universe is also populated with more conventional animals. These small animals are often used by Dr. Eggman as "organic batteries" to power his robot armies. The trapped animals can usually be freed by hitting the robot and destroying its metal case. In Sonic Adventure and Sonic Adventure 2, the small animals can be given to Chao, altering their appearance and attributes.

A Flicky is one of the most prominently used animals in Eggman's experiments. This small bird's first appearance in a game predates Sonic. Flicky and its respective game were alluded to in Sonic 3D Blast.

Music
Numerous composers have contributed music to the Sonic the Hedgehog series. Masato Nakamura of J-pop band Dreams Come True was responsible for the music of the first two 16-bit games. Ys/Streets of Rage composer Yuzo Koshiro composed the tunes for the first 8-bit game, except for what was retained from the 16-bit version. Sega's in-house music division, Sega Digital Studios, formerly known as Wave Master, have composed the majority of the music in later games. Jun Senoue, a member of the band Crush 40 and sound director of the series, has written and performed the main theme tunes of both of the Sonic Adventure games, Sonic Heroes, Shadow the Hedgehog, and Sonic and the Black Knight. Since the mid–2000s, the overall sound direction of the series has been handled by Tomoya Ohtani, who has served as the lead composer on Sonic the Hedgehog, Sonic Unleashed, Sonic Colors, Sonic Lost World, and Sonic Forces.

On several recent games, other non-Sega musicians have contributed music to the series. For example, Bowling for Soup lead singer Jaret Reddick performed the main theme of Sonic Unleashed, "Endless Possibilities"; and former Megadeth guitarist Marty Friedman played on "With Me", the final boss theme for Sonic and the Black Knight. Cash Cash lead singer Jean-Paul Makhlouf performed the opening theme to Sonic Colors, "Reach for the Stars", as well as the ending theme, "Speak With Your Heart". Hoobastank frontman Doug Robb performed and wrote the lyrics to the main theme of Sonic Forces, "Fist Bump".

Adventures of Sonic the Hedgehog
DIC Entertainment's Adventures of Sonic the Hedgehog is an American animated television series that was first broadcast in September 1993, and ran in cartoon syndication for a number of years afterward. It follows the escapades of Sonic and Tails as they stop the evil Dr. Ivo Robotnik and his array of vicious robots from taking over the planet Mobius. The plots very loosely followed the style of the early video games series, but focused very little on character development.

Sonic the Hedgehog (TV series)
DIC also produced the second cartoon series, called Sonic the Hedgehog (referred to as Sonic SatAM by fans to distinguish it from Adventures), which originally aired from September 1993 to June 1995. While Adventures of Sonic the Hedgehog is known for its bright colors and whimsical humor, Sonic the Hedgehog featured darker, more dramatic stories which still constitute a departure from the tone of most of the Sonic games. This adaptation follows Sonic and his fellow 'Freedom Fighters' who attempt to liberate Mobius from the grip of Robotnik, who plans to robotocise everything. The Sonic the Hedgehog comic book series by Archie Comics uses several characters from this series.

Sonic the Hedgehog (OVA)
A two-episode OVA series, based upon the game Sonic the Hedgehog CD and the video game series as a whole, was released in Japan in 1996. The episodes were combined and released in North America in 1999 under the name Sonic the Hedgehog: The Movie. It takes place on a world named Planet Freedom. It was the first to introduce an animated appearance of Knuckles the Echidna.

Sonic Underground
The cartoon Sonic Underground ran for 40 episodes in 1999. The last Sonic series from DIC Entertainment, produced by Les Studios Tex, the show has a similar premise to Sonic the Hedgehog, albeit in this version, Sonic is joined by two siblings, Manic and Sonia. Together they use the power of music to fight against Robotnik and eventually reunite with their mother.

Sonic X
Sonic X, an anime television series produced by TMS Entertainment, is the longest-running animated series based on Sonic to date, spanning a total of 78 episodes. Bearing much more similarity to the video game franchise, the series revolves around Sonic, his companions, and his enemies, being warped to the human world, where Sonic meets a boy named Chris Thorndyke, who helps him and his friends fight against Eggman. The series originally aired in Japan between 2003 and 2004, spanning 52 episodes, though an additional 26 episodes aired in France as early as 2005, and was licensed in North America and most other countries by 4Kids Entertainment. Saban Brands later claimed the license in 2012, but it was dropped in 2014.

Sonic Boom
In October 2013, Sega announced on its blog that a new computer animated series, Sonic Boom, is produced by OuiDo! Productions and will begin airing 11-minute episodes on Cartoon Network in Fall 2014. On February 6, 2014, Sega announced that Sonic Boom will become a separate franchise in the Sonic the Hedgehog universe. The new franchise includes two new Sonic Boom video games to preclude the TV series, and it uses redesigns of all the major characters exclusively within the franchise. Cartoon Network began to air the series starting from November 8, 2014.

Sonic Mania Adventures
Sonic Mania Adventures is a five-part series of animated shorts released on the Sonic the Hedgehog YouTube channel between March 30 and July 17, 2018, promoting the release of Sonic Mania Plus. The series depicts Sonic's return to his world following the events of Sonic Forces, teaming up with his friends to prevent Eggman and Metal Sonic from collecting the Chaos Emeralds and Master Emerald. The shorts are written and directed by Tyson Hesse, with animation production by Neko Productions and music by Tee Lopes.

Film
In August 1994, Sega of America signed a deal with Metro-Goldwyn-Mayer and Trilogy Entertainment to produce a live-action/CGI movie based on the Sonic the Hedgehog series, which would tie-in to the then-upcoming release of Sonic X-treme on Sega Saturn. A treatment was pitched to Sega by Richard Jeffries, titled Sonic the Hedgehog: Wonders of the World, in May 1995. Ultimately, the movie was cancelled as none of the three companies could come to an agreement on the deal. Jeffries, with the permission from Sega, later pitched his treatment to DreamWorks, but was rejected.

On June 10, 2014, Sony Pictures originally announced a new live-action/CGI hybrid film based on the Sonic the Hedgehog series. It is being produced by Neal Moritz on his Original Film banner alongside Takeshi Ito and Mie Onishi. Toby Ascher is executive producing, and the film is being written by Evan Susser and Van Robichaux. With Terminator 6, & Deadpool director Tim Miller being the producer, and Jeff Fowler directing. But on October 2017, Paramount announced that they had picked up the rights after Sony Pictures (Columbia Pictures) put the film into turnaround. However, most of the production team remained unchanged. It is being produced as a joint venture between Paramount Pictures, Original Film, Sega, Paramount Animation, Marza Animation Planet, and Blur Studio. The film is set for release on November 8, 2019. Jim Carrey will be playing the role of Dr. Eggman, James Marsden will play a police officer named Tom Wachowski, while Tika Sumpter and Natasha Rothwell are currently in unannounced roles. Ben Schwartz will voice Sonic in the upcoming film.

Sonic, Tails and Eggman appear in the 2012 Disney animated film Wreck-It Ralph. In the movie, Sonic has a small speaking role and Tails briefly appears as an image, while Eggman makes a non-speaking appearance. Sonic also has a small cameo in the 2018 film Ready Player One as a character avatar, and will return in the 2018 sequel to Wreck-It Ralph, Ralph Breaks the Internet.

Comics and manga
The Sonic the Hedgehog manga series, published in Shogakukan's Shogaku Yonensei was written by Kenji Terada and illustrated by Sango Norimoto. The manga, which started in 1992, was about a hedgehog boy named Nicky who can turn into Sonic the Hedgehog. Sonic fights Eggman, with Tails tagging along to help him.

Sonic the Hedgehog was an American comic series published by Archie Comics, which has spawned sister series Knuckles the Echidna (discontinued) and Sonic Universe. All of Archie's Sonic-related publications take place in the same fictional universe, which incorporates aspects of the video games and Sonic the Hedgehog: the Animated Series in addition to elements unique to that comic universe. Archie Comics also published a Sonic X comic book that supplemented the animated series of the same name. It began in November 1992 and was originally meant to be a four-part series; however, due to the positive reaction to the series' announcement, it was extended to ongoing status before the first issue premiered. The comic borrowed elements from the animated series' first two seasons and characters from the Sonic Adventure storyline. Some comics were published in the Jetix Magazine, in UK, Italy and Poland. In July 2017, Sega announced that they had ended their partnership with Archie, ending the series of comics after 24 years. Two days later, Sega announced that IDW Publishing would be releasing a new series of Sonic comics, starting in April 2018.

Sonic the Comic was a British comic published by Fleetway Editions between 1993 and 2002. Labeled "The UK's official Sega comic", in addition to Sonic the Hedgehog stories it also included comic strips based on other Sega games such as Ecco the Dolphin and Decap Attack. The main series of Sonic stories had their own unique storylines and characters in comparison to other Sonic media.

Reception and legacy
The Sonic the Hedgehog franchise was awarded seven records by Guinness World Records in Guinness World Records: Gamer's Edition 2008. The records include "Best Selling Game on Sega Systems", "Longest Running Comic Based on a Video Game" and "Best Selling Retro Game Compilation" (for Sonic Mega Collection). In the Guinness World Records: Gamer's Edition 2010, the Sonic the Hedgehog series was listed number 15 out of the top 50 video game franchises. In September 1996, Next Generation ranked the Genesis installments of the series (but not the Game Gear or Sega CD entries that had been released up to that time) collectively as number 20 on their "Top 100 Games of All Time", calling them "the zeitgeist of the 16-bit era". In December 2006, IGN ranked Sonic the Hedgehog as the 19th greatest series of all time, claiming that "although recent 3D entries in the series have been somewhat lacking, there is no denying the power of this franchise."

Neuroscientists studying the development of the embryonic neural system named a specific set of proteins, in charge of the differentiation of neural tube cells, after the main character of the game franchise.

A common criticism has been that the variant gameplay styles found in recent 3D games have strayed from the formula of the original series. Specifically, the series' jump to 3D has been noted as a declining point. In late 2010, Sega delisted several below-average Sonic games, such as the notoriously disliked 2006 game Sonic the Hedgehog, in order to increase the value of the Sonic brand after positive reviews for the games Sonic the Hedgehog 4 and Sonic Colors.