While many individuals at Sega had a hand in Sonic's creation, programmerYuji Naka and artist Naoto Ōshima are generally credited with the creation of the character, a blue 16-year-old anthropomorphichedgehog, who has the ability to run at supersonic speeds and the ability to curl into a ball, primarily to attack enemies. This is a major part of the gameplay of the series.
While Sega was seeking a flagship series to compete with Nintendo's Mario series along with a character to replace Alex Kidd as the company's mascot, several character designs were submitted by its AM8 research and development department. Many results came forth from their experiments with character design, including an armadillo (who later developed into Mighty the Armadillo), a dog, a Theodore Roosevelt look-alike in pajamas (who would later be the basis of Dr. Robotnik/Eggman's design), and a rabbit (who would use its extendible ears to collect objects, an aspect later incorporated in Ristar). Eventually, Naoto Ōshima's spiky teal hedgehog, initially codenamed "Mr. Needlemouse", was chosen as the new mascot. Sonic's blue pigmentation was chosen to match Sega's cobalt blue logo, and his shoes were a concept evolved from a design inspired by Michael Jackson's boots with the addition of the color red, which was inspired by both Santa Claus and the contrast of those colors on Jackson's 1987 album Bad; his personality was based on Bill Clinton's "Get it done" attitude. Sonic was created without the ability to swim because of a mistaken assumption by Yuji Naka that all hedgehogs could not do so. A group of fifteen people started working on the first Sonic the Hedgehog game, and renamed themselves Sonic Team. The game's soundtrack was composed by Masato Nakamura of the band Dreams Come True. Sega sponsored the group's "Wonder 3" tour, painting Sonic on the tour bus, distributing pamphlets advertising the game, and having footage of the game broadcast above stage prior to its release.
The original concepts gave Sonic fangs and put him in a band with a human girlfriend named Madonna. However, a team from Sega of America, led by Madeline Schroeder, who calls herself "Sonic's mother", "softened" the character up for an American audience by removing those elements. This sparked a heated issue with Sonic Team. Naka later admitted that it was probably for the best. Sonic's appearance varies greatly depending on the medium and the style in which he is drawn. In the video games, Sonic's original design by Oshima was short and round, with short quills, a round body, and no visible irises. Artwork featuring this design and drawn by Akira Watanabe was displayed on the package artwork for Sonic the Hedgehog, and most subsequent Sonic video games featured similar designs.
When Sonic the Hedgehog 2 for the Mega Drive appeared, Sonic's proportions changed. The original 1:2 head to height ratio changed to 1:2.5.
Beginning with Sonic Adventure in 1998, Sonic was redesigned by Yuji Uekawa as a character with longer legs and a less spherical body, longer and more drooping quills, and green-colored irises. Further subtle changes to the character's design have been made in subsequent games. Spin-off media such as comics and cartoons have featured variations on all these video game designs, with restrictions set by the standardized model sheets.
Sonic's first English game voice was provided by Ryan Drummond beginning with Sonic Adventure, a role he continued until 2004, when he was replaced by Jason Adam Griffith, who previously voiced the character in the American dub of the series Sonic X. Griffith was later replaced by Roger Craig Smith, starting with Sonic Free Riders and Sonic Colors in November 2010. In an interview, Drummond states he was offered the chance by Sega to re-audition for the role of Sonic, but rejected the role since it required him to quit his talent union.