Halloween 2020

Halloween in 2020 would be the fifth Halloween event in Pokémon GO.

Featured Pokémon
The following Pokémon were released with the start of the event:

Selected Pokémon had increased spawn rates in the wild and from Incense or Lure Modules:

These Shiny Pokémon were released with the start of the event: PS Gengar PS Gengar PS Sableye PS Spiritomb

There was also a chance to be photobombed by (these/this) Pokémon:

Timed Research
Trainers who completed Timed Research during Mega Buddy Challenge would access Halloween-themed Timed Research that would introduce Mega-Evolved Gengar.

Alolan Marowak Raid Day
On October, 2020, from 11:00 a.m. to 5:00 p.m. local time, Alolan Marowak will be appearing more often in raids.

Catch Mastery: Ghost Day
On October, 2020, from 8:00 a.m. to 10:00 p.m. local time, Ghost-type Pokémon will be appearing more often in the wild and there will be event-exclusive Timed Research available to complete.

Featured Pokémon
Selected Pokémon had increased spawn rates in the wild and from Incense or Lure Modules:

Trivia

 * This event was first mentioned in the blog about Mega September.