"Mummy ... why is the crazy lady asking for tricks? Where are our sweets?!"
Halloween was originally the Celtic holiday of Samhain, when people believed spirits and ghosts were able to travel between their world and ours on this one night. It was an honour if the spirits of relatives came to your door, and you were supposed to invite them in and provide them with food and shelter, while harmful spirits were kept at bay by wearing frightening masks and clothing. Fast forward several hundred years and we've turned that into mini witches and ghosts stuffing their faces with bagfuls of sweets. Not to mention the fact that its the only night where its totally acceptable to look like a slut and get away with it.
Free sweets and perfect reasoning to get drunk in a mini skirt ... God I love Halloween. :-)
My personal favourite...