Any number of things can go wrong when attempting a musical parody of The Exorcist. After all, William Friedkin’s 1973 classic horror movie was itself rumored to be cursed, having experienced more than its share of injuries and deaths during filming. Plus, it can be tricky finding the yucks in William Peter Blatty’s story, which takes blood and puke as seriously as it does Satan and the priesthood. Writer and performer Michael Shaw Fisher gives it a shot nonetheless with Exorcistic: The Rock Musical. Its dynamic cast is wholly committed to the bit and sing as if possessed, but Fisher’s script, which he began drafting in 2012, is convoluted to the point that audience members may be left wondering what the devil is going on.