Mawile did not originate from fanon, and the information on this page may not be entirely accurate to their canon. You may read more about this subject in the context of their canon on the following wiki(s):
Mawile are a Steel/Fairy type Deciever Pokémon that debuted in Generation III. It is the 69th Pokémon in the Hoenn PokéDex. Mawile are short yellow and black Pokémon. They have a yellow bottom to make it seem like they are wearing a dress and their feet and arms are black.
Mawile is one of a handful of Pokémon that can access Mega Evolution. The required Mega Stone is called Mawilite.