Leslie Nielsen disproved the adage that American lives have no second acts. After decades as a rather stolid, unexciting leading man in genre pics like “Forbidden Planet” (1956) and “The Plainsman” (1966), Nielsen inserted his serious, authoritative persona into the parody-based comedies of the Zucker brothers and enjoyed a highly successful second act in films like “Airplane” (1980) and especially the “Naked Gun” series (1988, 1991, 1994), as well as “Scary Movie 3” (2003) and “4” (2006). The key to the silver-haired leading man’s success was his deadpan delivery and seeming obliviousness to