A new advertisement for Pokémon GO's upcoming event, GO Fest 2021, has revealed four new costumed Pokémon: top hat Galarian Ponyta, Galarian Zigzagoon, Gardevoir, and Flygon.
While we now know what they look like, we don't know much about these costumed Pokémon yet outside of what Niantic initially wrote in the GO Fest 2021 announcement. The full costumed Pokémon announcement Pokémon GO posted is as follows:
Pikachu Rock Star or Pikachu Pop Star—your choice will determine the in-game music that will play for you during the event. The Pokémon music producer Junichi Masuda has produced brand-new tracks just for Pokémon GO Fest 2021, including a rock-and-rolling track for Pikachu Rock Star fans, a high-energy electro-pop song for Pikachu Pop Star stans, and more! You'll also get to fill out the rest of your musical group! Will you pick Galarian Ponyta or Galarian Zigzagoon? Gardevoir or Flygon? All these Pokémon will be dressed to impress in special event costumes!
Now, what players are going to wonder, of course, is if these Pokémon will be available in their Shiny forms. While we cannot officially confirm, personally, I'd be shocked if they weren't. If these weren't released in their Shiny forms, and that means all four of them, they'd essentially be one-and-done catches. The only time that Niantic didn't allow a costumed Pokémon to be Shiny in recent years was Top Hat Kirlia for the Fashion Week Event, which I fully believe was a mistake on their part that wasn't caught, as the Shiny sprite was in the game. So I do very much believe that we'll be able to encounter Shiny Galarian Ponyta, Galarian Zigzagoon, Flygon, and Gardevoir in these new costumes.
Now, the other question is whether or not they will be able to evolve. This question, of course, applies to Ponyta and Zigzagoon only as the others are fully evolved. Again, while we have no confirmation, it's quite likely based on recent patterns that these won't be evolvable.