“Pikachu Parties in Pokemon GO! Keep your eye out for a special Pikachu wearing a party hat to celebrate Pokemon Day!” Pokemon Day, for those unaware, is usually held on the 27th of February, and is a day dedicated to special events based around Pokemon.
Pikachu is ready to lead the Pokemon Day celebration in Pokemon GO. From February 26 at 1:00 p.m. PST to March 6 at 1:00 p.m. PST, any Pikachu you encounter in the wild will be wearing a festive party hat! The Pikachu you catch during that time will keep its party hat forever, so be sure to look for this special Pikachu during its short time in the wild.”