Halloween costumes, now central to modern trick-or-treating and embraced by both children and adults, have evolved from traditional frightening figures to include popular media characters. Their deep historical roots trace back to ancient Celtic festivals like Samhain (October 31st), which marked the beginning of winter and was seen as a liminal time when spirits and the dead could more easily interact with the living. During these pre-Christian and early Christian observances, people wore costumes to either ward off evil spirits or impersonate them and the souls of the deceased, often in exchange for offerings or protection. By at least the 16th century, these customs developed into "mumming" and "guising," involving individuals going door-to-door in disguise, reciting verses for food. This practice, along with the Christian tradition of "souling" (collecting "soul cakes"), gradually shaped the beloved costume-wearing tradition we recognize today.