The name "Miles Prower" is a pun on "miles per hour", a reference to the famed speed of the Sonic the Hedgehog series. He is an 8-year-old orange-golden yellow, anthropomorphic fox with two tails (similar to the mythological kitsune), hence the nickname. He is known to be Sonic's sidekick and a mechanist. He is able to use his two tails to propel himself into the air like a helicopter for a limited time. His debut was in October 16, 1992, introduced in the 8-bit version of Sonic the Hedgehog 2; the 16-bit version was released that November.
During his first appearance in Sonic the Hedgehog 2, his fur was an orange color, but the color was changed to yellow-orange for Sonic Adventure, and light-yellow for Sonic Heroes. In 1993 and 1995, he starred in his own games, Tails and the Music Maker for the Pico, Tails Adventure, and Tails' Skypatrol for the Game Gear. Tails is the third most popular character of the series, behind Sonic and Shadow, according to official polls.
Yamaguchi ended up with a compromise. He sneaked the name "Miles" in as his legal name; "Tails" would be his nickname, ending up with the full name of Miles "Tails" Prower.
In the American Sonic comic book, along with the Adventures of Sonic the Hedgehog and Sonic the Hedgehog cartoons, he was originally a brownish color, but the comic artists eventually decided to change this to match his in-game appearance.
Tails made his third major appearance in 1994 when Sonic 3 was released, this time acquiring the ability to pick up Sonic and use his tails to fly him to other areas, rotating his tails like a helicopter. He also gained the ability to swim under water, something Sonic has never been able to do.
Tails has also starred in games without Sonic. His first solo game was Tails' Skypatrol, which is a puzzle-like game for the Game Gear released exclusively in Japan. This was followed by Tails Adventures later the same year, which is a Metroid-esque platformer with RPG elements. Tails is also the star of Tails and the Music Maker for the Sega Pico.
In later games, Tails has had roles that require unique modes of play. For example, in Sonic Adventure, Tails is one of the six playable characters and his gameplay is standard platforming stages, but the goal of each stage is to get to the Chaos Emerald before Sonic, or to the missile dud in the final race against Dr. Eggman.
In the sequel to Sonic Adventure, Sonic Adventure 2, he is featured in third-person shooting segments, seated in his "Cyclone" mech. This third-person shooter style of play, along with Dr. Eggman's shooting levels in the same game, were very similar to the E-102 Gamma levels of Sonic Adventure.
Tails has appeared either as a playable character or in a supporting role in almost all later Sonic titles. He still often resumes his role flying other characters around, such as in Sonic Heroes, where Tails appears on Team Sonic as their flight-type character, being capable of carrying both Sonic and Knuckles.
He is also seen in the background of Green Hill Zone along with Silver the Hedgehog and Knuckles in Super Smash Bros. Brawl He also appears as a trophy. He has been confirmed to appear in the upcoming Sonic Unleashed..
While Tails is indeed useful to Sonic in many situations, he can be a hindrance. Because he is very young and cannot defend himself, he is incredibly susceptible to kidnappings. Sonic appears to know of this flaw and does his best to protect him, but his protection methods are often the reason why Tails gets kidnapped in the first place. He also seems to have a very large appetite, and like Sonic, his favorite food is chilli dogs, but apparently Tails likes extra cheese on his (in the anime and games, his favourite food is mint candy).
He became a full "member" of the Freedom Fighters near the end of Season 2. In the canceled Season 3, it was rumored that his relationship with Sonic would draw closer to that of the video games.
Tails later completes part of the Great Harmony by sealing away the Chaos Emeralds in a special dimension after being captured by A.D.A.M.. He also soon manages to rescue his parents along with Sonic, but it causes a riff between the two that they eventually settle. Tails has feeling for Fiona Fox, and he is shown to have married Mina Mongoose and had two children in Mobius: 25 Years Later.
In the third season of Sonic X, Tails is the commanding officer of the Blue Typhoon, and over the series develops leadership. Tails becomes attracted to and eventually falls in love with Cosmo, a plant-like female alien introduced during this season. The strength of Tails's love is shown in Episode 73, where Shadow, in an attempt to kill Cosmo, clobbers Sonic, Chris, and Knuckles, but, despite his best efforts, can't manage to get past Tails despite severe beating and threatenings, who is determined to protect Cosmo no matter the cost. He had an emotional breakdown when he was forced to kill Cosmo himself to stop the Metarex after which he received a seed from Sonic which was the last remaining part of Cosmo.
Tails has been described as a mechanical prodigy who rivals Dr. Eggman, however he has yet to realize his full potential. Additionally, by spinning his two tails like a helicopter rotor, he has the unique ability to push himself through the air to catch up with Sonic. However, when he takes to flight, he tires quickly. Tails is also able to swim by dog paddling.
Like many Sonic characters, Tails can transform into a Super Form, but needs the Super Emeralds instead of the Chaos Emeralds. He also has other transformations in media beside the games (such as Turbo Tails). However, he hasn't appeared in a super form since his transformation in Sonic Heroes. His only official transformation is seen in Sonic the Hedgehog 3 & Knuckles, in which he gains a white aura and several Flickies protect him.