You can’t catch spooky, scary skeletons in a Pokeball, but if you’re looking to celebrate Halloween, then Niantic has something planned for you. Pokemon GO will have a Halloween 2020 event that will take last October 23rd to November 3rd. More Ghost-type Pokemon will appear, and you’ll earn double the candy from catching and transferring Pokemon.
Gengar and Sableye are receiving Halloween costumes. You can find the former’s in raids, and the latter either in eggs or by encountering them in a wild battle. Spiritomb can be found through Normal Research, and you’ll have a chance of getting a Shiny one. Meanwhile, some Special Research tasks called “A Spooky Message Unmasked” can get you Galarian Yamask, and you can get Mega Gengar through Timed Research by collecting Gengar Mega Energy.