PIKACHU20
PLEASE NOTE: You will only be able to use this code once! The date you choose to enter the code will determine which hat and move set your special Pikachu will have. This means you're going to have to be very careful when deciding on which Pikachu you wish to add to your party. Study the schedule below, and get ready to choose your Pikachu!
•19/9/17 – 25/9/17: Original hat (Kanto and Johto regions)
•26/9/17 – 2/10/17: Hoenn region hat
•3/10/17 – 9/10/17: Sinnoh region hat
•10/10/17 – 16/10/17: Unova region hat
•17/10/17 – 23/10/17: Kalos region hat
•24/10/17 – 30/10/17: Alola region hat
https://www.pokemon.com/uk/pokemon-news/a-new-movie-and-a-ne…
Check here for info on each one
https://www.serebii.net/events/dex/025.shtml