Mew was secretly added to the original Pokémon games by programmer Shigeki Morimoto.
Morimoto inserted Mew near the end of development after debugging features had been removed, leaving enough space for one additional Pokémon. The character was not intended to be obtainable through normal gameplay and was initially known only within Game Freak.
Mew’s hidden presence became a major source of rumors among players. Nintendo and Game Freak later promoted special distributions, including a 1996 CoroCoro Comic campaign that selected 20 winners to have Mew added to their cartridges.
Mew is numbered 151 in the original Pokédex and is classified as a Mythical Pokémon. It is often confused with Mewtwo, but Mewtwo is a separate species created in the fiction as a genetic experiment based on Mew.