The festival celebrated in October that involves costumes and candy is Halloween. Halloween has its origins in the ancient Celtic festival of Samhain, marking the end of the harvest season and the beginning of winter. It evolved to include various traditions, such as dressing in costumes to ward off spirits, trick-or-treating for candy, and carving pumpkins into jack-o'-lanterns. Modern Halloween, celebrated on October 31st, has become a commercial phenomenon, with parties, haunted houses, and themed decorations taking center stage. This festive occasion is enjoyed by children and adults alike, promoting creativity and community engagement.