The original 1996 Mew lottery selected 20 people. CoroCoro Comic announced a special Mew promotion in Japan, and twenty winners were chosen from readers who submitted postcards.
Mew was a secret, last-minute addition to Pokémon Red and Green. It was not normally obtainable through standard gameplay, and its existence was initially hidden from most players. The promotion allowed winners to send in their game cartridges so Mew could be added to them.
The event generated enormous interest because Mew was numbered 151 and was absent from the ordinary in-game adventure. It also helped create the idea that Pokémon could be distributed through real-world events. Mew is often confused with Mewtwo, which is number 150 and is obtainable later in the original games. Mewtwo is a genetically engineered Pokémon connected to Mew in the games' story, while Mew is the mythical species that completed the original Pokédex.