Anime fans rejoice! A low-key One Piece reference has been added to Pokémon GO in the form of a hat. For a limited time, Pikachu will wear a special Straw Hat and the same hat can be found in the Style Shop.
From July 22 until July 29, players can discover a rare Pikachu variant, wearing a straw hat. A matching hat can be purchased for the player avatar in the Style shop
While never said, this appears to be a reference to One Piece, a popular adventure anime/manga about a band of pirates led by Luffy D. Monkey. The protagonist character is known for their straw hat.
Evidence of this can be seen all over the official announcement:
If you enjoy collecting Pikachu wearing amusing hats in Pokémon GO, there’s still one piece to that puzzle that you need. Luckily, the latest in the grand line of behatted Pikachu is arriving soon in the form of Straw Hat Pikachu!
From July 22, 2019, at 1:00 p.m. through July 29, 2019, at 1:00 p.m. local time, this special Pikachu will appear in the wild, giving Trainers plenty of chances to add it to their crew. Pikachu’s kicky straw hat is perfect for keeping the burning sun at bay during these sunny summer months. If you want to coordinate your avatar’s outfit with Pikachu, there will be a matching straw hat available in the Style Shop.
You’re sure to treasure this new addition to your team, so don’t miss out—get ready to head out on another grand Pokémon GO adventure!
It sounds to me like they really wanted to do this cross-promo, but couldn’t get the green light by VIZ Media, the organization that owns the rights to One Piece. Either way, we’re into it.