In June 2021, a special loading screen has been made available. Featured Pokémon include Meloetta, Jigglypuff, Plusle, Minun, Loudred, Galarian Ponyta, Galarian Zigzagoon, Bidoof, Jumpluff, Lillipup, Purrloin and Chatot. These Pokémon are enjoying music together, referencing the core theme of Pokémon GO Fest 2021. A new version of this loading screen will be implemented following the firs day of Pokémon GO Fest 2021. The updated version also features the addition of the Mythical Pokémon Hoopa in its Confined form.
Source: Pokémon GO