Mewthree

Mewthree is possibly one of the most famous fake Pokémon. It appears commonly in fake cheats and fan fiction.

One rumor suggests that after all 150 Pokémon are captured in the Pokédex in Pokémon Red and Blue, returning to the Cerulean Cave where Mewtwo was found and using Rock Smash on a rock 50 times would make a Lv. 99 Mewthree appear. This, of course, is impossible, as Rock Smash was not introduced until Generation II, and Pokémon with moves not available in Generation I were unable to be traded back.

On obtaining Mewthree in Cerulean cave it has the following moves:-

Psychic (move), Future Sight, Recover and Safeguard

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.