Pokémon GO will celebrate Professor Willow with the Willow’s Birthday Research event on July 21 from 10 a.m. to 8 p.m. local time. The limited-time event marks the Pokémon GO debut of Professor Willow’s assistant Pikachu, with Trainers also having a chance to encounter its Shiny version. Players can take part in free Timed Research and event-themed Field Research to earn encounters and additional rewards throughout the day. With a brand-new costumed Pikachu, exclusive research and special activities, Willow’s Birthday Research is shaping up to be a fun one-day celebration for Pokémon GO Trainers.
Source: Official Pokémon GO blog