According to PR for this inaugural production, Theatre 5.2.1 plans to burn each original script after the tenth and final performance because its work is “like a match struck in a dark room illuminating, exposing, then burning out.” That kind of self-importance doesn’t bode well, but this original musical, created by the ensemble with music by Dan Schiller, is a goofy exercise free of pretension. It breaks no new ground but provides a pleasant showcase for the players, as an avaricious slumlord moves into his building, begins waging war against the mice, and eventually loses his grip on reality. The cast, ably directed by Lewis Lain, has a ball with the show, which is like Marc Blitzstein agitprop crossed with the feel-good harmonies of Joe “Sesame Street” Raposo. The Sleeper doesn’t necessarily illuminate, but at least it doesn’t induce slumber. Through 4/16: Fri-Sat 10:30 PM. Theatre Building Chicago, 1225 W. Belmont, 773-327-5252. $5.