It's supposed to be a childish scary way of begging for candy and also a tradition to celebrate this particular holiday.Thye knock the doors of the neighbours' houses and "Trick-or-Treat" them, i.e. asking for candies. Well, for us Muslims, we have the very same tradition, yet it occurs in the Holy Month of Ramadan where children stroll around the neighbourhood moving from one house to another for candy. This tradition is called (Gergai'an -قرقيعان OR Khesher- خشر). It is a friendly way to celebrate the coming of Ramadan.