"Get ready for the Violence of the Lambs," promises the tagline, and Black Sheep does not disappoint: In their dietary preference, King's little lambs lean more toward intestines than ivy. They're victims of genetic engineering on an isolated Kiwi farm, where ruthless Angus Oldfield (played by Peter "Get Me a Bruce Campbell Type!" Feeney) plans to revolutionize the livestock industry with his poppin'-fresh "Oldfields." Not even the arrival of his brother Henry (Nathan Meister), a queasy city slicker afflicted with sheep-aphobia, halts Angus's plans to unveil the new breed before visiting globo-investors.

Greed may create the contamination, but as in 28 Days Later, it takes self-righteous green activists to loose it upon the world—in this case, a top-knotted wanker named Grant (Oliver Driver), who swipes a fetal Sheep Zero from the farm. His "Meat Is Murder" bumper sticker doesn't deter the newborn from gnawing off his ear, leaving his accomplice—earthy-crunchy Experience (Danielle Mason)—to make her way across miles of suddenly hostile farmland. The fetus finds the flock, and soon their fleeces too are flecked with human flesh.

Much has been written about the resurgence of various horror genres to exorcise the world's ills—zombie movies acting out the threat of military occupation, torture-porn shockers that freely examine our culpability in coercion. It can't be a coincidence that monster movies such as Black Sheep, South Korea's The Host, and Ireland's mad-cow thriller Isolation are making a comeback at a time of grave concern over genetic monkeying and dawning environmental catastrophe. They're the squirrelly down-low cousins of An Inconvenient Truth—tagged, if you'll recall, as "the scariest movie you'll ever see"— no less than Hostel Part II is the sleazy bizarro-world kin of A Mighty Heart.

But Black Sheep, which is less accomplished than The Host and goofier than the glum Isolation, has no high-minded pretense. It's cloned from the warped DNA of fellow New Zealander Peter Jackson's Dead Alive, all gory hyperbole and blood-spewing sight gags. (Jackson's Weta effects outfit handled the many maulings and nifty sheep monsters, with nods to the icky transformation scenes from Joe Dante's The Howling.) The grotesquerie of appetite ("My haggis!") sets up many of the sickest jokes—as when King cuts from a scene of vegan traitor Grant chomping a cuddly bunny to the world's most viscous can of spaghetti plopping into a pot. "Have you been eating meat, Grant?" Experience accuses her beau, who's morphed into eight feet of man-hungry were-wool. "Was it even organic?"

But the main source of humor is the disconnect between the blank, impassive sheep (which bleat as if dubbed by Mercedes McCambridge) and their murderous means—which are as startling to us as they are to the movie's ill-fated Sinister Scientist. (He laughs too, until two poofy marauders festoon his innards across the barnyard.) King milks his blobby forms for incongruous menace, even staging a parody of Rod Taylor's tiptoe-through-the-toucans in Hitchcock's The Birds. And what fun's a cast of surly sheep if you can't treat them like woolly piñatas, beating them on trees, pounding their heads on steering wheels, and detonating their atomic farts with the flick of a lighter?

The cartoonish overkill that often makes Black Sheep a hoot proves wearying over an entire movie: The broad comedy and one-note characters eventually cancel out the horror, leaving elaborate set pieces that are more frantic than funny. But writer-director King deserves credit for wringing every ounce of ovine mayhem from his sheep-for-brains premise. There is no such thing as an unfunny cutaway to a sheep.