Niantic has announced the April Fool event which takes place on Thursday, April 1st, 2021, from 12:00 a.m. to 11:59 p.m. local time.

BREAKING: Pokémon mischief is on the rise, and Team GO Rocket has an Aipom problem

Trainers, The Tricky Pokémon event is back, and mischievous Pokémon seem to be causing more trouble than usual! Throughout Thursday, April 1, 2021, Pokémon prone to mischief will be appearing more often in the wild—some of them may even be Ditto in disguise! Some of them appear to be causing trouble for Team GO Rocket, too, so it’s the perfect time to complete Team GO Rocket Timed Research and rescue Shadow Zapdos from Giovanni’s clutches!

Date + Time
Thursday, April 1, 2021, from 12:00 a.m. to 11:59 p.m. local time

Features

• Pokémon prone to mischief—like Aipom, Croagunk, and Purrloin—will be appearing more often in the wild!
• Sources tell us that Team GO Rocket Grunts will only have Shadow Aipom on their teams during the event. They thought catching Aipom would put a stop to their pranks—but how wrong they were!
• Team GO Rocket will be appearing more often at PokéStops and in balloons.
• The Team GO Rocket Timed Research launching during this event will be available from Thursday, April 1, 2021, at 12:00 a.m. to Thursday, April 8, 2021, at 11:59 p.m. local time. Complete it within that time to earn a Super Rocket Radar and other rewards!
• The switch timer in the GO Battle League will be cut in half! Could this be more Pokémon mischief at work?
• Take a few snapshots for a surprise!
• Ditto will be appearing more frequently in the wild during the event, so be sure to catch Pokémon that Ditto are known to transform into! We’ve also received reports of Ditto transforming into one more Pokémon species than before, and it seems this phenomenon will continue after the event concludes.

Please be aware of your surroundings and follow guidelines from local health authorities when playing Pokémon GO. Upcoming events are subject to change.

Source: https://pokemongolive.com/post/trickypokemon-2021/?hl=en