The event lasts from October 20th at 8 PM BST to November 2nd at 9 PM BST. You'll see an increased number of spooky Pokémon, including Gastly, Cubone, Misdreavus and Houndour. The developer promises even more Pokémon from Ruby and Sapphire as early as December. Not only that, but Pikachu will be out and about in costume, just begging you to catch him. Players will double their candy rewards for catching, hatching and transferring Pokémon during the event, and your special buddy will get candy twice as fast as usual. The in-game shop will have Raid passes and Super Incubators in special boxes, while players will get to purchase Mimikyu's Disguise Hat for their avatar.