Why was Birthday Pikachu banned?

The card's name is the first joke: it is printed as "_____'s Pikachu," with a blank line, because the card is a birthday card. You write your own name in the blank, and lower down there is a second line, "Your Birthdate: ______," for the date. Its attack, Birthday Surprise, does 30 damage, unless it is your birthday, in which case you flip a coin for 30 plus 50 more. Wizards of the Coast banned it immediately upon its English release, for the reason every schoolchild spots at once: nothing stops a player from declaring that today is their birthday. It stands with Ancient Mew as one of only two cards banned even from the Unlimited format, where nearly everything is legal.

The original is Japanese: an unnumbered promotional card, illustrated by Kagemaru Himeno, tucked into the All Card Calendar released on November 5, 1998 for the card game's second anniversary. English speakers met it in 2000 as Wizards Black Star Promo 24, first in the Pikachu World Collection sold at Pokémon Park 2000 in Sydney, printed there with a gold foil Pikachu tail stamp. Japan reprinted it in 2001 with new artwork in the sixth volume of the manga How I Became a Pokémon Card, and in 2021 the original returned again in the Celebrations Classic Collection for the 25th anniversary.

The sequels moved the joke into the stores. A jumbo Birthday Pikachu, illustrated by Atsuko Nishida, was given out at the Tokyo Pokémon Center to visitors who came on their birthday and proved it with a birth certificate; its attack, Happy Birthday, orders your opponent to hand you a card from their collection as a present. From November 2010 the Pokémon Center Birthday Campaign ran the idea annually, with jumbo prints by Kanako Eo (2010, with a gold foil HAPPY BIRTHDAY stamp) and Naoki Saito (2012), given to visitors within a week of their birthday alongside a game download and a store coupon. A card you can only receive on your birthday, that only works on your birthday: the most honest promo ever made.