You know those ”Saturday Night Live” skits that, somewhere around the third sexual pun, lose sight of the punchline and drag on and painfully on? Well, those stinkers ain’t got nothin’ on Corky Romano, a train wreck of a movie about a clumsy, clueless dork (Kattan, who else?) who masquerades as an F.B.I. agent to keep his Mafia family from going to the slammer. The insipid dialogue and flimsy plot development are grating, but it’s the witless filler stuffed everywhere in between that puts one over the edge. Do us a favor, Chris — stick to Mango.