Sonic the Hedgehog

Sonic the Hedgehog is the main character of SEGA's  franchise, and the main mascot of the company itself. He was created to show off how quickly the SEGA Genesis could move and change sprites. In his games, he is usually focusing on defeating his main enemy Dr. Ivo Robotnik, also known as Dr. Eggman, with the help of his many allies. In the McLeodGaming media, Sonic is an antagonist serving as a guardian to Bowser in the flash-animated shorts serial, A Super Mario World. Notably, he is also playable in both games of the Super Smash Flash series: Super Smash Flash and Super Smash Flash 2.

Character description
SEGA wanted a game capable of competing with Mario and a character to replace Alex Kidd as the company's mascot. Several character designs were submitted by its AM8 research and development department, including an armadillo, a dog, a Theodore Roosevelt look-alike in pajamas (which would later be the concept for Dr. Ivo Robotnik, known also by his alias Dr. Eggman), and a rabbit. 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, 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 Bad, while his personality was based on Bill Clinton's "Get it done" attitude. The character was created without the ability to swim because of a mistaken assumption by Yuji Naka that all hedgehogs could not do so. Sonic's first appearance in the video game world was in the racing game Rad Mobile (later ported to the SEGA Saturn under the name Gale Racer), but Sonic's first major appearance was in the platform game  for the SEGA Mega Drive/Genesis, which also introduced his nemesis Dr. Robotnik. A group of fifteen people started working on the first Sonic The Hedgehog game, and renamed themselves Sonic Team.

The original concepts had Sonic with fangs and 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 these, sparking a heated issue with Sonic Team, although Naka later admitted 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 quite 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.

Beginning with Sonic Adventure, in 1998, Sonic was redesigned by Yuji Uekawa as a taller character with longer legs and a less spherical body, longer and more drooping quills, the addition of shoe buckles, 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.

Different actors have provided the voice for Sonic in his game appearances. Sonic originally had a few voice samples in Sonic CD, but the actor is unknown. Sonic's first true voice actor was Takeshi Kusao for the arcade game SegaSonic the Hedgehog, with Junichi Kanemaru continually voicing the role beginning with the release of Sonic Adventure. Sonic's first English voice actor was Jaleel White (better known to fans as Steve Urkel on the TV show Family Matters) in the animated series The Adventures of Sonic the Hedgehog, and the Sonic the Hedgehog Saturday morning show, and Sonic Underground. 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 Anthony Griffith, who previously voiced the character in the American dub of the anime series, Sonic X. With the start of the recent Sonic games (Sonic Colors and Sonic Free Riders), Jason was replaced by Roger Craig Smith, who is the actual voice actor for Sonic.

In A Super Mario World
Sonic appears in the second episode of the A Super Mario World series along with Knuckles, both serving as Bowser's guardians. Sonic and Knuckles' reason for working for Bowser is that they wanted to prove SEGA characters are better than Nintendo characters (which is ironic as Bowser is a Nintendo character) by challenging Mario and Link in a fight. Sonic briefly escapes the battle after Knuckles is defeated by being pushed into the lava. Mario and Link chase after him to the next room, where Sonic transforms into Super Sonic (even though he used one single Chaos Emerald). Super Sonic briefly has the upper hand against Mario and Link but when he prepares to give them the final blow, he is attacked and defeated by Cloud Strife, who attacks him from behind. He is not seen afterwards.

In Super Smash Flash
Sonic is among the numerous playable characters in the original Super Smash Flash. It is noteworthy to point that Sonic got a playable appearance in this fan game before his actual playable debut in an official  game. He is distinctively a starter character. He, as many other characters, had only 5 different attacks all derived from Sonic Battle.

In Super Smash Flash 2
Sonic returned in Super Smash Flash 2 as a veteran. Most of Sonic's moves are taken directly from Super Smash Bros. Brawl,, Sonic the Fighters, and Sonic Battle, and his sprites are completely custom-made. He has the best ground mobility in the game. He is ranked 32th of C+ tier on the current tier list.

Trivia

 * Sonic is among the four characters who made it as playable characters in the  series before their actual confirmation as playable characters in the official Super Smash Bros. series, the other three being Cloud Strife, Meta Knight, and Mega Man.