Tickets are available for BOO! at the Zoo, Knoxville’s largest Halloween event. BOO! at the Zoo features safe and not-too-scary fun scheduled over three weekends; Thursday through Sunday, Oct. 19-22 and Oct. 26-29, from 5:30 p.m. - 8 p.m. each evening. BOO! at the Zoo, a Halloween tradition for 31 years, is a family event featuring trick-or-treating through the zoo along the BOO! Trail, the Chick-fil-A Monster Mash tent with fun that’s perfect for preschool and elementary-aged kids, friendly costumed characters and entertainers throughout the zoo.