Oct 28, 29 & 30: 5:30-8:30 p.m. It’s no trick, only the sweetest treat: Boo at the Zoo, Smithsonian’s National Zoo and Conservation Biology Institute’s beloved family-friendly Halloween event, sponsored by Mars Wrigley Confectionery. Tickets include special after-hours access for animal viewing at the Elephant Community Center, Small Mammal House, Reptile Discovery Center, Great Ape House and Think Tank, dance party, a souvenir tote bag and around 30 trick-or-treat stations around the Zoo. Tickets.