Community Day is an event that Niantic will include in Pokémon Go every month
In each monthly event, there will be a different Pokémon with an exclusive move. On Pokémon Go Community Day it will be an opportunity for trainers to meet up in the parks. And thus make new friends and experience what it means to be part of the Community.
The special Pokémon will appear frequently for a few hours. If you catch him he will learn a special and unique move, also during this event other bonuses will be available, such as XP or Stardust, Bait Module, etc..
The first day of this event will be Saturday January 20 and he will have Pikachu as a special guest but in his surfer version, he will know the surfing movement, something logical.