The Detroit Zoo’s annual “merry-not-scary” Zoo Boo celebration returns this Halloween season, featuring a festively decorated half-mile trick-or-treat trail through the front of the park. Presented by National City, Zoo Boo will be held on the evenings of October 19 to 21 and October 25 to 31 from 6 p.m. to 8 p.m., rain or shine.