In Pokémon Legends: Arceus you can receive Pikachu and Eevee Masks by having a save file from previous games in the mainline Pokémon game series.
The games in question are Pokémon: Let's Go Pikachu and Eevee and, with their save files safely stowed on your Nintendo Switch, these cosmetic items will be yours.
Having save files from other mainline Pokémon instalments on your console will also allow you to catch Darkrai and the Modern Team Galactic clothing set. You can also encounter Shaymin (Land Forme) and earn the Shaymin Kimono Set by having a save file from another set of Pokémon games.
If you'd like to learn more, visit our Pokémon Legends: Arceus walkthrough.
How to get the Pikachu and Eevee Masks from Pokémon: Let's Go Pikachu and Eevee in Pokémon Legends: Arceus
First things first - you can only receive the Pikachu and Eevee Masks if your Nintendo Switch contains a save file from either Let's Go Pikachu or Eevee. It doesn't matter which game you have a save file for, because, either way, you'll earn both masks.
Next, you need to play Pokémon Legends: Arceus to the point where you've joined the Galaxy Expedition Team, which will take you roughly one hour.
Our Pokémon Legends Arceus walkthrough will help you pick a starter Pokémon and win the Kleavor boss fight. You’re also tasked with filling the Hisui Pokédex by obtaining new evolutions like Kleavor by evolving Scyther, Wyrdeer by evolving Stantler, Sneasler by evolving Hisui Sneasel and Overquil by evolving Hisui Qwilfish. There’s a host of new evolution methods, including ones for the Eevee evolutions. Take the time to complete Requests too, such as The Sea’s Legend, Wurmple’s Evolved! and finding the Wisp locations. Don’t forget to track down every Unown location too.
Now all you have to do is visit the clothier in Jubilife Village and, there, you'll be able to earn both the Pikachu and Eevee Mask.
Have fun exploring the Hisui region in Pokémon Legends: Arceus!