“Corky Romano” isn’t actually another of those excruciating elongations of “Saturday Night Live” sketches that have proliferated on the big screen in recent years; it just feels like one. It’s coarse, clumsy and interminable, the lameness of its script matched only by the ineptitude of its execution. In the misbegotten effort to meld “Ace Ventura” and “Analyze This,” Chris Kattan–the TV show’s resident antic munchkin–plays a “new” character, but hardly an original one. He’s a sweet-natured but utterly dimwitted veterinarian recruited by his long-estranged mob father (Peter Falk) to infiltrate the FBI and destroy the evidence the agency has assembled against the old man. Unfortunately the computer hacker who’s contrived his false identification as Agent Pissant (the moniker, endlessly repeated, gives you a good idea of the quality and level of invention in the script) has made the bumbling Corky into a purported super-sleuth, and he’s therefore given all sorts of important assignments he repeatedly screws up–with invariably fortunate results that only enhance his legendary status, of course.

Maybe Corky could have worked as a recurrent SNL sketch figure (after all, viewers always need dead time to wander off and fetch a drink from the fridge), but when his adventures are extended over a ninety-minute span in a theatre, they grow tiresome indeed. It doesn’t help that he’s impersonated by Kattan, an incessantly manic fellow whose bug-eyed intensity and curiously creepy quality exhaust more than they entertain. Kattan was awful in “A Night at the Roxbury,” in which he paired with the equally unsettling Will Ferrell, and he was gruesomely unfunny as the revivified corpse that stalked the latter portion of “Monkeybone,” but here, required to carry a whole feature on his own, he proves well-nigh insufferable. Simply put, he lacks the sweetness and charm such a doltish character needs to sustain an entire movie–the quality provided, for example, by Rob Schneider in “The Animal” (to cite just another SNL second banana), or by Adam Sandler. By contrast Kattan seems the potentially amusing supporting guy transferred unwisely into the lead.

That isn’t to say that he doesn’t have physical dexterity (or, to be more accurate, physical abandon). He throws himself into the innumerable pratfalls and reams of slapstick with a ferocity that makes you wince at the thought of the damage he must be doing to his slight frame. But in terms of humor, the strenuous effort is unavailing; “Corky Romano” is far from funny, whether the poor fellow is trapped in an electrified mask, transformed into a quivering mass of jello by an accidental dose of drugs, running backward with his arm caught in the window of a car traveling in reverse, kicked in the puss by a martial-arts midget, dressed up as a girl scout, or humiliated in the innumerable other ways the perpetually puerile script demands. It’s quite bad enough while the narrative remains a chaotic chain of ineptly staged comic bits, but things get really grim toward the close, when the plot drags sentimentality and romance into the mix. A big revelation at the close, moreover, is about as idiotic a twist as a writer could devise.

The picture is also very poorly directed by first-time helmer Rob Pritts. A good deal of the slapstick stuff seems clumsily improvised, and many sequences have a thoroughly amateurish look, badly framed and sloppily shot. This doesn’t help Kattan, and the rest of the cast fares even worse. Peter Berg is grossly overwrought as one of Corky’s oafish brothers, and as the other Chris Penn looks as though he’s wearing a fat suit–but isn’t. As for Falk, he did the same mob figure to far better effect in the recent “Made.” (Isn’t it time that someone designed one final “Columbo” for him, showcasing that far more lovable sleuth in one last case?)

Over the years “Saturday Night Live” has introduced a lot of young comics who have tried to segue onto the big screen. A few of them have lasted; most haven’t. On the evidence of “Corky Romano,” Chris Kattan will fall into the latter category.