Since January 28, 2025, a Shiny Manaphy event has been released in Pokémon Home in celebration of the third anniversary of Pokémon Legends: Arceus. This Manaphy can be redeemed in the mobile version of Home if the player has the Sinnoh Pokédex from Brilliant Diamond and Shining Pearl complete. There is no need to have all Pokémon in BDSP deposited at the same time.
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December 1, 2017 to April 30, 2018. That was the most recent way to obtain Manaphy IN THE US. Otherwise, from July 13 - 22 2018, you could get it in South Korea.