https://www.gamespot.com/articles/pokemon-go-players-can-catch-a-special-pikachu-for/1100-6457013/

February 27 is Pokemon Day, and like last year, Niantic is celebrating the occasion by giving players a chance to capture a rare Pokemon in Pokemon Go. For the next few days, players will be able to encounter a special Pikachu, which will come with an exclusive move it cannot typically learn in the mobile game.

From now until 1 PM PT / 4 PM ET on February 28, players will have a chance to capture a Pikachu wearing a party hat, similar to the one available during last year's Pokemon Day celebration. This time around, however, the party hat Pikachu will know the move Present. In addition to that, players will earn triple the usual amount of Stardust they receive for each special Pikachu they capture.