To celebrate "Pokémon Day" next week, there will be Pikachu running around the game wearing "festive party hats." Pokémon Day is intended to be a celebration of the day in 1996 that the first Pokémon games came out in Japan. In addition to Pokémon GO, the celebration will extend to the Pokémon website, Pokémon Trading Card Game, and more. The party hat Pikachu will be available in Pokémon GO from February 26 at 1:00 pm PST to March 6 at 1:00pm PST. You'll come across Pikachu in Pokémon GO that are wearing party hats.

Source: Forbes February 24, 2017 00:41 UTC