Pokemon/Shadow Pokemon: Shadow Pocket Monster.
Name: Mewtwo. Now that it is a Shadow Pokemon, people have begun to refer to it as Mewthree.
Species: Mewtwo.
Shadow or Normal?: Shadow.
Alignment:

Need I explain?
Appearance: PMC is being stupid and not letting me post links or pics. It's just Mewtwo, but with darker colors.
Moves: I dunno. Would Mewtwo have the normal four move limit? I mean c'mon, it's effing Mewtwo! Like the king of all things Pokemon. (Screw Arceus.)
I'd probably say:
Shadow Ball
Psystrike
Psychic
Shadow Rush
Level: About 90?
Backstory:
Long, long ago, Team Rocket discovered a Mew living in Guyana. Later, to search for fossils as ordered by the new leader, Giovanni, Team Rocket went back to the area. When searching for fossils, they found an eyelash belonging to Mew. Giovanni asked Dr. Fuji to clone the Mew using the eyelash. Wanting to use the research funds to clone his dead daughter, Amber, Fuji agreed.
Mewtwo, the clone of Mew, was successfully created a month later, and was stored on New Island. At this point, Mewtwo was not fully grown, and was living in a test tube alongside Ambertwo, believed to be asleep. However, it was telepathically communicating with Ambertwo, very much awake. Ambertwo unfortunately died, human life force not being as strong as a pokemons. Bulbasaurtwo, Charmandertwo, and Squirtletwo, (Pokemon being cloned with Mewtwo) also died, suggesting Mewtwo had a more powerful life force than other Pokemon. (Man, there’s red squiggles all over the place here!) Eventually, Mewtwo fully matured and broke out of his test tube. Those responsible for his creation were happy that they succeeded in their goal of creating the world's most powerful Pokémon. Enraged and confused about the circumstances that led to his creation and powers, Mewtwo attacked the scientists on New Island. Despite the efforts of security systems that attempted to control him, Mewtwo destroyed the island and all the scientists on it.
Immediately thereafter, Giovanni found Mewtwo and convinced him to help with Team Rocket's goal of controlling the world. Mewtwo's power was focused, as well as weakened and controlled, by a robotic suit of armor as he performed tasks such as battling under Giovanni within the Viridian Gym and helping Team Rocket capture Pokémon. Eventually Mewtwo became tired of being used by Giovanni.
Mewtwo developed a strong hatred for humans, and thought that they were weak and selfish beings only interested in power and wealth; he also despised the Pokémon who served humans. He escaped from Giovanni, destroying Team Rocket headquarters in the process, and relocated to his birthplace on New Island, where he built his own headquarters. Mewtwo then issued a challenge to several strong Pokémon Trainers, including Ash Ketchum. He used his powers to create a storm that would serve as a test to see who could make it to the island. Only a handful of Trainers managed to brave the storm and arrive, including Ash and his friends. Upon revealing himself, Mewtwo challenged the Trainers with a Venusaur, Blastoise, and Charizard (all cloned) to prove his superiority to human Trainers and the superiority of cloned Pokémon to trained Pokémon.
To do this, he used a variation of the Poké Balls used by Trainers. Once caught in the Balls, the Pokémon that had been brought to the island were cloned in an upstairs laboratory. However, before Mewtwo could defeat the Trainers and move out into the world, Mew appeared. (You still reading this?) The two Pokémon fought and ceased battle when Ash was caught in their crossfire and turned to stone. After Ash is revived by the tears of the nearby Pokémon, clone and original alike, Mewtwo experiences a change of heart and stops his destructive rampage.
Wanting to find himself, Mewtwo erased the memories of those present and he and his clones left New Island for Johto, eventually settling on Mt. Quena. During this time, presumably to prevent any chance of any humans encountering them, it frequently enclosed the mountain with a severe storm. However, it isn't willing to allow a bus full of humans to die from being knocked off course, using his telekinesis to place the bus back on the road, namely because that would result in more humans arriving to investigate for, and help, any survivors, thus making it even more risky.
A few years later, Giovanni found Mewtwo's hiding place via one of their satellites and began a plan to capture him once again. However, this plan was foiled when Mewtwo again met with Ash, who did not remember their previous encounter. Giovanni restrained Mewtwo, but his friends helped him to escape and defeat Giovanni. At the end of the ordeal, Mewtwo erased Giovanni and his soldiers' memories of him, and decided to move throughout the world searching for the meaning of his life.
When Mewtwo found out about the Shadow Pokemon, it decided to fight back. It helped fight back the Shadow Pokemon the first time, but was careless, and got captured the second time that they came back. It took awhile, but Mewtwo was converted into a Shadow Pokemon, and now is fighting with the Shadow Pokemon, just a tiny hint of goodness lying dormant in the back of his head. He is pretty much the strongest Shadow Pokemon out there.
Anything Else?: PUUUUURPLE PINEAPPLES! His favorite food.