They come around at random too, but I don't think they give pelt/mask/antlers unless it's Halloween. A few years ago I remember Halloween to be a lot creepier with tons of fog, giant mushrooms and the time of day was night. At the moment it's day but since there is candles about my theory is that they will come around later today to make it darker so the candles are alight. I think they might also appear later to make everything normal again once the celebration ends, but that's just a guess.