Opening night on Monday will mean the end of Mr. Friedman’s mad dashes to the C train to juggle rehearsals; 11 days later, “Mr. Burns, a Post-Electric Play” begins previews at Playwrights Horizons. It is Mr. Friedman’s eighth collaboration with the Civilians, each of them directed (and in many cases created) by Steve Cosson. This piece, written by Anne Washburn, brings a macabre twist to the real-world interviews that have been a crucial component of Civilians pieces like “Gone Missing” and “In the Footprint.”Here, people’s hazy post-apocalyptic memories of one episode of “The Simpsons” yield the last surviving piece of culture, which morphs by the late-21st century into a surreal, pop-music-infused pageant."