This event was distributed to players with a 3DS of US, EU or TW regions, via common serial code.
The code was accurately guessed to be PIKACHU20, hours before its reveal on official sites.
The same code can be used to redeem other variations of this Pikachu, provided your save file hasn't received one via wonder card.
The variations receivable follows a schedule.
Format Ver.1.0.5-3, Post Updated Date:20171003_1121