Sonic the Hedgehog (Japanese:ソニック・ザ・ヘッジホッグ) is the flagship character for video game, arcade game (and one-time home game console) company Sega, which has released a series of video games in which he either stars or plays a role. Sonic was competeing head-to-head with Nintendo's mascot Mario for over a decade until Sega went out of the home console market. He now lives on in various Nintendo and other consoles.
Sonic replaced Alex Kidd, who was Sega's mascot prior to 1990. Naoto Oshima designed the character while Yuji Naka was the main programmer. He would later become head of the Sonic Team division.
Sonic is a blue hedgehog who lives on the planet Earth (Mobius in various American sources). He has the ability to run very fast. His blue pigmentation was explained in an issue of gaming magazine Gamepro as being the result of getting caught in an explosion involving cobalt, but this is probably not canonical. There is an alternative explanation in Stay Sonic: Official Sega Handbook, a book about Sonic the Hedgehog written by Mike Pattenden. At some point it was divulged (probably from an American source) that Sonic enjoys eating chili dogs.
The premise of the games revolves around Doctor Eggman (Doctor Ivo Robotnik in the earlier releases in North America and Europe) trying to take over the world by turning the animals into robots called Badniks. Sonic is charged with saving them. In later games he is joined by Miles "Tails" Prower, Amy Rose, Knuckles the Echidna, Cream the Rabbit and a host of others.
In SatAM and Archie Comics, Sonic is in love with Princess Sally.
Interestingly, one of a class of genes involved in fruit fly embryonic development, called hedgehog genes after the name given to the first member of this class discovered, has been named sonic hedgehog after this character.
Games involving Sonic the Hedgehog
Key
For the Sega Megadrive/Sega Genesis:
For the Sega Master System:
For Sega Mega-CD/Sega CD:
For the Sega Game Gear:
For the Sega Pico:
For the Sega 32X:
For the Sega Saturn:
For the Sega Dreamcast:
For the PC:
For SNK Neo Geo Pocket:
For Nintendo Game Boy Advance:
For Nintendo Gamecube:
For Sony Playstation 2:
For Xbox:
For Arcade:
Leaked prototypes
Games Sonic Characters have cameoed in:
Pirated games which are not from above starring Sonic the Hedgehog
Public domain
Television Series
Comic Books
Sonic Manga and Sonic Doujinshi have also been released in Japan