Eevee

Eevee (イーブイ Eievui) is a unique -type Pokémon that can evolve into one of seven forms. These forms are: Jolteon, Flareon, Vaporeon, Espeon, Umbreon, Leafeon and Glaceon.

Appearance
Eevee is a mammalian creature with brown fur, a bushy tail that has a cream-colored tip, and a furry collar that is also cream-colored. Eevee has brown eyes, big ears, and pink paw pads. Its design appears to be based specifically on the fennec fox, a small fox like animal that are found in desert like areas. It and its evolutions also has traits of raccoons, foxes, dogs, and cats. Eevee is said to have an irregularly shaped genetic structure, enabling it to evolve into multiple Pokémon. Eevee are quite rare, but are able to live almost anywhere, as they may evolve to suit their surroundings. It's possible moves are: Tackle, Tail Whip, Helping Hand, Sand-Attack, Growl, Quick Attack, Bite, Baton Pass, Take Down, Last Resort, and Trump Card.

Special Abilities
Eevee can have either the ability Runaway or Adaptability. Runaway is an ability that will allow the user to run from any wild Pokémon battle, negating the effects of moves that prevent running away. Adaptability increases the users STAB from x1.5 to x2.0. Eevee are Pokémon with unstable genetic codes. This gives them the ability to evolve into seven different evolutions triggered by the environment, time of day, or the usage of evolutionary stones.

In the Anime
In the anime, Eevee first appeared in The Battling Eevee Brothers. A little boy named Mikey was hiding the Evolution Pokémon from his three older brothers because they wanted him to evolve it. However, when Mikey's Eevee single-handedly defeated Team Rocket, they were able to accept the fact that Mikey wanted to keep his Eevee just the way it is. Ash's longtime rival Gary Oak uses an Eevee of great quality that eventually evolves into Umbreon. May has an Eevee that hatched from an egg, which she used in Pokémon Contests all across the Kanto and Johto region. When May traveled to Sinnoh, she took it to Route 217 to evolve into a Glaceon. The Kimono Girls who first appeared in the Pokémon Gold and Silver games, also make an appearance with their Pokémon (all of which are evolutions of Eevee) in Trouble's Brewing. The youngest of the Kimono girls had an unevolved Eevee (the only of the sisters to have one) in this episode though it later evolved into an Espeon later on in the episode "Espeon, Not Included".

In the Manga
In Pokémon Adventures, Red is in possession of an Eevee which had been experimented on by Team Rocket. As a result, it could transform back and forth from the three evolutions Vaporeon, Jolteon, and Flareon along with its base form, allowing it greater tactical ability in fighting other Pokémon. Eventually, it evolved into an Espeon, losing its special ability to interchange abilities. In the Electric Tale of Pikachu manga, the character Mikey (who appeared in the anime episode: "The Battling Eevee Brothers") makes an appearance with his own Eevee and within the chapter that he appears in, Mikey attempts to prove to his brothers that he doesn't need to evolve his Eevee to win battles.

Evolutions
Eevee are very unique in that they can evolve into seven different types of Pokémon. The first three evolutions that were introduced during Generation I of the game series, require the use of Evolutionary stones.

During Generation II, two more evolutions were added, Espeon and Umbreon, with requirements of evolution being in either day or night time.

Due to the absence of a time feature in Generation III, these two evolutions were not obtainable in the games. Umbreon and Espeon were in the Pokedex and Eevee was available in the games, but only by trading it over from Pokemon FireRd and LeafGreen or Pokemon Colosseum by breeding either Umbreon or Espeon with a Ditto.

In the Generation IV games, an additional two evolutionary forms were added, Leafeon and Glaceon. Different from the previous ways to evolve Eevee, the trigger for these evolutions requires that an Eevee levels-up near either the Moss Rock in Eterna Forest or the Ice Rock on Route 217.

In Pokémon XD: Gale of Darkness, the times of day are represented by the Sun Shard and Moon Shard, respectively, and, since said game features no in-game clock, they replace the time requirement for these two evolutions.

Pokédex Entries
Is also a possible choice for the hero in Pokemon Mystery Dungeon Red, Pokemon Mystery Dungeon Blue, and Pokemon Mystery Dungeon Explorers of the Sky.

Trivia

 * So far, Eevee is one of three Pokémon (the others being Tyrogue and Kirlia, unless you count all of Burmy's forms as one Pokemon, and Wormadam as a different Pokemon) to have more than one evolution, one of two (the other being once again Tyrogue) to have three or more, and the only Pokemon that has 4 or more.
 * Eevee is a common Gift Pokemon.
 * Its name is a palindrome, meaning its name is spelled the same backwards as it is forward. Only two other Pokemon share the same trait, namely (Ho-Oh and Girafarig).
 * Eevee is the only Pokemon that can evolve into several other Pokemon using multiple element stones.
 * As seen in the Pokemon Special Eevee was a Pokemon that had undergone genetic mutation (Team Rocket is at fault) allowing it to evolve the de-evolve and evolve agian. It is noted that it went from Jolteon to Flareon to Vaporeon. and then back to Eevee. This power was available through an ear device that causes harm to Eevee as it evolved or de-evolved. It became a normal Eevee after being captured by Red.
 * In the manga, Red had a special Eevee that can go back to it's original form after evolving, but when it evolved into an Espeon, it didn't change back to it's original form.