A slightly more subtle example involving Frank is that he's more than willing to turn two innocent humans, his own creation, and his groupie into mindless sex-slaves and force them to perform a stage show against their own will.
Frank's final song "I'm Going Home", with the sudden appearance of a crowded audience cheering him on as he tearfully absorbs all the attention they're giving him. Then the song ends, and it's implied that the audience is nothing more than a figment of Frank's imagination. It helps to show just how crazy Frank really is and is quite eerie to that effect.