The title of this farce about an overeager security guard (Kevin James) suggests a one-joke trudge. But Paul Blart: Mall Cop has a few surprises in store. The biggest is James, an unexpectedly nimble master of the face-plant, the failed jump, and the lopsided tumble. The former King of Queens star also proves to be a warm leading man who grounds the movie as it morphs into a loopy heist thriller after a promising start as something entirely different: a gentle comedy of suburban underachievement. B

