It was stated earlier this afternoon on Reddit that the Shiny forms of the entire Pikachu family were found in the source code of the latest update, Pichu included.
Invites to see the event live are extremely rare and no details have been so far been teased. Well, here is everything about it in a nutshell. It is celebrated to felicitate Pikachu and hundreds of Pikachu descend dancing and parading for the tourists. Unfortunately, the said pocket monster is only available in the Land of the Rising Sun.
More recent months have seen the reveal of new shinies, including Shiny Pikachu, suggesting more creatures will see unique variants over time. Mr. Mime (a regional-exclusive Pokemon usually seen in Europe) is spawning at the festival, and the game has set up two parks with rare spawns. Since it's a Japanese event, the time zones are going to be challenging.
Meanwhile, the release of Legendary Pokémon Zapdos had its Shiny look as the default appearance, seemingly by accident. Aside from a bug fix with the raid system, shiny Pokémon are also reportedly coming to the game.
Ditto pretending to be Shiny Pokémon aren't Shiny themselves - that's right, if you find yourself a rare Shiny Magikarp and it suddenly transforms into a Ditto, the Ditto itself won't be Shiny. What began as a pretty bare bones experience has since added Gen 2 Pokemon, Legendaries, and even shiny Pokemon.