Today is the official first anniversary of Pokemon GO, and the celebration includes swaths of wild Pikachu roaming about wearing the famous hat that Ash left Pallet Town in. These Pikachu will be taking their hats off after 1 PM PDT on July 24, but if you catch one before that, as it was with the party hat wearing Pikachu, it will keep its famous headgear, and even wear it as Raichu once it evolves. On top of the special Pikachu, the celebration includes the availability of a limited-edition Anniversary Box. Inside each box, you'll find an assortment of in-game items including incubators, max revives, ultra balls, and raid passes. As a side note, Pokemon GO players have thus far caught a whopping 125 billion Pokemon.
The hat-wearing Pikachu should begin appearing at 1 PM PDT today. Niantic did not announce the price for the Anniversary Box, and it does not appear to be on sale just yet. It will likely drop at the same time as the special Pikachu. While this development likely means that the shiny Pikachu that players were expecting won't be part of the anniversary event, or at least won't come out to play just yet, it is still present in the game's code, so it will almost certainly come eventually. The series of events both in-game and in the real world that serve to celebrate the game's first year don't end until after the "Pikachu Outbreak" event in Yokohama, Japan, set to take place in August, which means that shiny Pikachu still have plenty of chances to appear. It's also entirely possible that the shiny Pikachu is already an active and catchable Pokemon, just an extremely rare one.
The day after this event ends on July 21, Niantic will be holding the first Pokemon GO Fest in Chicago. After that, there will be a presentation at this year's Siggraph festival, which is said to include an announcement of some sort. Tickets to the Chicago event are sold out at this point, but all players will still be able to reap rewards earned during the festival. Niantic has yet to announce what those rewards are, of course. Finally, for those who won't be able to venture out of their hometown in the near future, another Nest Migration event, where certain Pokemon or certain types are seen in larger numbers for a while, is expected to happen on July 12, based on the timing of previous Nest Migrations.