I am always sniffing around for the pagan holdover in the fabric of our monothestic culture.
No greater holdover exists than Halloween. Folded into All Souls Day or All Saints Day, the overtly pagan element of the holiday is evident. Anyone who has gone to work at 7AM knows that the days are growing shorter, darker, colder. Anyone in the North East of North American can see that nature is doing its great slough of vegetation. In heavy wind and soggy rain, leaves tumble down to death.
We are at a threshold where life cascades into death, or at least, to the dormancy of life. And at this time, somewhere in the past, certain cultures saw in this death in nature a metaphor for the greater cycles of human life and death. So this holiday of Halloween, or the Day of the Dead, was created in part to fulfill a great need: the desire to have a nexus between life and death. A place where the dead communicate with the living.
The costumes and trick-or-treating are really just a superficial symbols for the expression of these greater archetypes. Things die. But death also brings forth new life. And this is a great cycle that never ends