Mew was promoted through CoroCoro’s 1996 “Legendary Pokémon Offer.”
Mew was a secret Pokémon added late in the development of Pokémon Red and Green. It was hidden in the games but could not normally be obtained through standard gameplay. The promotional campaign appeared in the April 1996 issue of CoroCoro Comic, shortly after the games launched in Japan.
Twenty randomly selected winners could send their cartridges to Nintendo so Mew could be added to their games. The promotion received more than 78,000 entries, far exceeding Nintendo’s initial expectation of 3,000. This helped create rumors about an unseen Pokémon and encouraged continued interest in the games.
Mew is often confused with Mewtwo because their names and designs are related. Mewtwo, however, is a separate Pokémon with a major role in the first animated movie. In the Pokédex, Mew is number 151, while Mewtwo is number 150.