On Halloween your villagers will give you candy which you can exchange for furniture from the Creepy or Spooky furniture sets.
Speak to Jack to exchange your candy; note that the villagers will all be wearing Pumpkin masks like Jack so you’ll have to search for him!
You can collect candy from 6pm to midnight from villagers wandering outside their houses and inside their own houses. The villagers outside their houses will play a mini-game with you.
If you win, you’ll get your candy. If you lose, you’ll put on the pumpkin mask or an item (ragged clothing or jack-in-the-box) will appear in your inventory.
Villagers inside their homes will need to be scared before they give you any candy. This means that you’ll need to wear a mask when you knock on their doors.
Give candy to Jack for a chance to receive one of these horrifying prizes (if you fork over a lollipop, you’re guaranteed a prize):