A common example of a well-known fake Pokémon is Mewthree. It appears commonly in fake cheats and fan fiction.
Rumors of Mewthree's existence within the Pokémon games have circulated since the first generation. Many fake methods were created, that were often impossible to perform or resulted in the player deleting their save file. These stories have led to a number of hack games focusing on this unofficial Pokémon. The most notable of these is Pokémon Chaos Black, in which Mewthree can evolve into another fake Pokémon, Mewthree X.
Mewthree was also one of the names given to the silhouette of Lucario early after its release on many internet forums because it appeared strikingly similar to Mewtwo.
Although it was a fake Pokémon, it was given an official mention in Mewtwo Strikes Back, where the scientists responsible for creating Mewtwo, commenting on the success of its creation, decided to start making Mewthree. However, the plans never got beyond this due to Mewtwo's destruction of the lab on New Island.