Halloween is more Irish than St. Patrick's Day somehow. Halloween origins come from a Celtic festival for the dead called "Samhain." Celts believed the ghosts of the dead roamed Earth on this holiday, so people would dress in costumes and leave "treats" out on their front doors to appease the roaming spirits. Cats, bats and spiders are all symbols of Halloween because in the Middle Ages people thought witches would and use them to do their bidding.