The practice may have originated in a Celtic festival, held on 31 October–1 November, to mark the beginning of winter. It was called Samhain in Ireland, Scotland and the Isle of Man, and Calan Gaeaf in Wales, Cornwall and Brittany. The festival is believed to have pre-Christian roots. After the Christianization of Ireland in the 5th century, some of these customs may have been retained in the Christian observance of All Hallows' Eve in that region—which continued to be called Samhain/Calan Gaeaf—blending the traditions of their ancestors with Christian ones. It was seen as a liminal time, when the spirits or fairies (the Aos Sí), and the souls of the dead, could more easily come into our world. It was believed that the Aos Sí needed to be propitiated to ensure that the people and their livestock survived the winter.
Some group costumes can be tough to put together because they nearly require the right number of folks. Fortunately, the crew of the Mystery Machine has solved this problem, too! Team up as the Scooby Squad, since they're always splitting up in teams. While Scooby and Shaggy are off getting into trouble, Velma, Fred, and Daphne are great for a group of 3 Halloween costumes! When it's time to finish the episode, bring everyone together and unmask that ghost!