Four dead guys are coming to Downtown Pittsburgh just in time for Halloween. Only these aren't the typical zombies one might expect for a show opening on the second scariest night of the year. (See this week’s Election Guide for a preview of the first.) The members of the all-male singing group in Pittsburgh CLO’s production of Forever Plaid return to life not to eat the brains of unexpected passersby, but for the performance of a lifetime. The musical comedy features the goofy barbershop quartet performing classic 1950s hits. (Expect lots of crooning.) The show marks an anniversary for both the show and the cabaret theater — Forever Plaid was the very first show performed 15 years ago at the Greer Cabaret Theater and opens this year’s season.