Hedgehog

Hedgehogs in the video game, comic book, and television series fiction of the Sonic the Hedgehog series, are anthropomorphic, spiny animals with quills of varying styles, similar to human hairstyles. Sonic, the main character of the series is a hedgehog followed by other hedgehogs through the series.

Hedgehogs are frequently brightly-coloured (despite being mostly brown or grey in real life). They also often (but not uniformly) possess special abilities including, but not limited to, Speed (Sonic), Telekinesis (Silver) or the abilty to use Chaos Control (Shadow).

Several robotic hedgehogs also existed, most of whom were created by Doctor Eggman in imitation of Sonic. The most famous of these is Metal Sonic.

Games
In the games, neither the bright colours nor special powers of the hedgehogs are explained (save for Shadow, whose abilites derive from the circumstances of his creation).

Hedgehogs in the games

 * Sonic the Hedgehog
 * Amy Rose
 * Shadow the Hedgehog
 * Silver the Hedgehog
 * Mephiles the Dark - in appearance only

Hedgehogs in Sonic and the Black Knight

 * Sir Lancelot
 * Sir Galahad
 * Nimue, Lady of the Lake

Robot hedgehogs

 * Silver Sonic
 * Mecha Sonic
 * Metal Sonic
 * Metal Sonic 3.0
 * Shadow Androids
 * Robo-Sonic

Comics
In the Archie Comics, the bright colours of the hedgehogs are inherited traits. Sonic's blue pigmentation originates from his family (his parents and his uncle are also blue). That said, Amy and Rob O' the Hedge are cousins, yet one is pink and the other is green, for no discernable reason. In Sonic the Comic, most hedgehogs are brown. Sonic and Amy both were born brown, and gained their distinctive colours later due to accident and mutation.

Hedgehogs in the Archie comics

 * Sonic the Hedgehog
 * Bernadette Hedgehog
 * Jules Hedgehog
 * Sir Charles Hedgehog
 * Amy Rose
 * Rob O' the Hedge
 * Shadow the Hedgehog
 * Silver the Hedgehog
 * Scourge the Hedgehog
 * Rosy the Rascal
 * Manik Acorn
 * Cyborg Sonic
 * Zonic the Zone Cop

Robot hedgehogs in the comic
See also Sonic robots in the Archie comic
 * Sir Charles Hedgehog (When he was a Robian)
 * Jules Hedgehog (Robian)
 * Pseudo Sonic
 * Metal Sonic
 * Metal Scourge
 * Silver Sonic
 * Silver Sonic II
 * Mecha Sonic (Roboticized Sonic)

Hedgehogs in Sonic the Comic

 * Sonic the Hedgehog
 * Amy Rose
 * Super Sonic (independent entity)
 * Cosmic the Hedgehog*
 * Tonic the Hedgehog*
 * Bravehog
 * * Both were actually Metamorphia in disguise.

Robot hedgehogs in StC

 * Metallix
 * Silver Sonic
 * Badnik Sonic

Cartoons
Different variety of hedgehogs in the cartoons, Only in Sonic X and the movie. the colour of Sonic's blue colour is not explained, in the rest it is an inherited colour accept in Sonic underground where all his family members have their own colour.

Hedgehogs in the Adventures of Sonic the Hedgehog
Regular brown hedgehogs were also seen in the series. In the episode 50 "Robotnik's Pyramid Scheme" Professor Canine Stein shows Sonic his family tree of blue hedgehogs but they were never named, however some of Sonic's ancestors were named.
 * Sonic the Hedgehog
 * Cute little Hedgehog in a polka dot bikini (from "Blackbot the Pirate (episode)")
 * Buff Male Hedgehog in a speedo (from "Blackbot the Pirate (episode)")
 * Penelope
 * Masonic
 * Mummified Hedgehog

Merhogs: half hedgehog, half fish animals.

 * Merna the Merhog
 * Queen of the Merhogs
 * Merhogs of Mertopia

Robot hedgehogs in AoSTH

 * Pseudo-Sonic
 * Breezie

Hedgehogs in the Sonic the Hedgehog (TV series)

 * Sonic the Hedgehog

Robot hedgehogs in SatAM

 * Sir Charles Hedgehog (Robian)

Hedgehogs in the Sonic Underground

 * Sonic the Hedgehog
 * Manic the Hedgehog
 * Sonia the Hedgehog
 * Queen Aleena the Hedgehog
 * Aman-Rapi
 * The Royal 'Corrupt' Hedgehogs
 * Fat alternate version of Sonic as a king
 * Greedy alternate version of Manic as a king
 * Vain alternate version of Sonia as a queen
 * Luke Periwinkle
 * Unnamed purple hedgehog girl, usually seen homeless

Robot hedgehogs in Underground

 * Sir Charles Hedgehog (Robian)
 * Hip