The Mythical Pokémon Mew will be available in the Poké Ball Plus, and players will be able to transfer it to their version of Pokémon Let’s Go Pikachu and Let’s Go Eevee. To unlock Mew in your game, all you need to do is connect to the Internet with your activated Poké Ball Plus. This offer doesn’t require a subscription to Nintendo Switch Online. However, it won’t be available for long, so Nintendo recommends doing it as soon as possible before it expires. The Poké Ball Plus will be available to purchase alongside the upcoming Nintendo Switch games on November 16.
Source: @Pokemon
Pokémon Blog 
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