Twenty CoroCoro readers were randomly selected in the original Mew giveaway. The promotion was announced in the May 1996 issue of the Japanese magazine and offered winners a Mew added to their Pokémon cartridge.
Mew had been included as a hidden, last-minute addition to Pokémon Red and Green. It was not normally obtainable through standard gameplay, which made the giveaway especially mysterious to players. Entrants submitted postcards, and the selected winners sent in their cartridges so Mew could be uploaded.
The promotion helped create rumors and word-of-mouth around the games. Although Mew was the 151st Pokémon, players initially had little official information about it, strengthening the impression that the games contained secrets beyond the visible Pokédex.