Trick-or-treating—going from house to house in search of candy and other goodies—has been a popular Halloween tradition in the United States and other countries for an estimated 100 years. But the origins of this community-based ritual, which costumed children typically savor while their cavity-conscious parents grudgingly tag along, remain hazy. Possible forerunners to modern-day trick-or-treating have been identified in ancient Celtic festivals, early Roman Catholic holidays, medieval practices and even British politics.