Works on Sun, Moon only. You get Pikashunium Z as well which works if you missed the previous events for the capped Pikachus.
PIKACHUM20
Enter that via the code option to redeem. Enjoy ^_^
No known code for any second Pikachu aside this Kanto cap Pikachu.
NOVEMBER 23 IS THE LAST DAY THIS CODE WORKS.
North American and Japan games only.