Mr. Warmth: The Don Rickles Project offers a conventional nonfiction look at the insult-spewing comedy legend, comprised of myriad film, TV, and live performance clips, as well as a cavalcade of yesteryear and present-day celebrities who gush about the iconically combative star. Director John Landis's documentary is formally unadventurous, and barely interested in its subject's upbringing or the roots of his humor; in the film's doting view, there is no great subtext, no great mystery, to Rickles's success or appeal, which is chalked up to the obvious fact that the man is naturally hilarious. Anecdotes flow freely but more impressive is the sight of Rickles-a nearly 50-year vet of Las Vegas-bringing down the house during a 2007 routine at the Golden Nugget Hotel and Casino, in which the 81-year-old displays his gift for working a room by laying into his audience with all manner of unscripted (albeit time-honed) inappropriate and/or offensive comments, many of them out-and-out racist.