The original Mew lottery randomly selected 20 winners.
Mew was a secret Pokémon added late in the development of Pokémon Red and Green. It was not normally obtainable through standard gameplay, which made its existence a source of rumors among players. The promotional campaign gave fans a legitimate way to receive it on their game cartridges.
CoroCoro Comic announced the “Legendary Pokémon Offer” in its May 1996 issue, published on April 15. Readers sent in postcards, and 20 entrants were chosen at random. The winners then sent their cartridges to have Mew uploaded onto them.
The promotion helped generate word of mouth at a time when Nintendo had not expected the games to become a major hit. By September 1996, sales of Pokémon Red and Green had exceeded one million units. Mew’s unusual distribution also helped establish the series’ tradition of special-event Pokémon.