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

Rumors of Mewthree's existence within the Pokémon games have circulated since the first generation. 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. 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.

does anyone have the code for mewthree

I do have a "code for Mewthree" and you can PM me to get it. A few things you should know first. It is NOT in ANY way a legit pokemon. It is simply a hacked creation. DO NOT use it in online play or use it in any form other than single player mode please.