Spooky, Halloween-themed acts, pop-up performances and a haunted maze backstage are just the beginning of the fun at “Muni Mayhem,” happening Oct. 11-13 at the Muni Opera. An official announcement promises everything from “ballet zombies to Jack Skellington and the Addams family” will be present for the fundraising event. “You can spend the entire evening at The Muni taking in the shows, going through the maze and enjoying some time by the fire,” said Muni board of managers president Michelle McLaughlin. Admission is $10 for adults, $5 for children ages 3-12 (no charge children under two). There will be two stage performances scheduled for 7:30 p.m. and 8:45 p.m. each night, with pop-up performances taking place in various spots throughout the grounds. Coffee and hot chocolate will be available, along with s’mores around a campfire.