Mew was revealed through a 1996 CoroCoro lottery promotion after the first Pokémon games launched.
Mew was a last-minute addition to Pokémon Red and Green and was not normally obtainable through ordinary gameplay. In April 1996, CoroCoro Comic announced a promotion in which 20 randomly selected winners could send in their cartridges to receive Mew.
The secret Pokémon generated rumors and encouraged players to keep discussing the games after release. Mew is often confused with Mewtwo because the names are related, but Mewtwo is a separate Pokémon created through genetic experimentation and featured prominently in the first movie.