They’re pulling the wool over your eyes

New Zealand, the bawdy saying goes, is where men are men and sheep are nervous. But in Jonathan King’s horror comedy “Black Sheep,” it’s humanity’s turn to shiver and shake. Transformed by a renegade geneticist from docile balls of cotton to bloodthirsty mutants, the film’s four-legged flesh-eaters run riot over a sprawling family farm, sending its inhabitants scattering like, well, sheep.

Following in the footsteps of Sam Raimi and fellow New Zealander Peter Jackson, King mixes slapstick humor with gushers of gore. Bodies are ripped to pieces, intestines pulled out, lips bitten off, each piece of tattered flesh lovingly crafted in latex by New Zealand’s Weta Workshop.

The reliance on physical rather than digital effects may speak as much to the movie’s budget as its artistic aims, but it instills “Black Sheep” with a kind of bloody nostalgia, a longing for the days when a severed head couldn’t be simulated with the click of a mouse.

The sheep’s metamorphosis is masterminded by Dr. Rush (Tandi Wright), a typically nefarious but strangely fetching mad scientist. Tasked by the rancher Angus Oldfield (Peter Feeney) with genetically engineering a softer, woollier breed, she’s taken matters into her own hands, with predictably dangerous results. The job of halting the resultant rampage falls to Angus’ brother Henry (Nathan Meister), who has been absent from the farm for 15 years. The reason? A crippling case of “ovinophobia,” which he describes as “the completely unfounded and irrational fear that one day this was going to happen.”

The bad doctor has help from a pair of inept animal-rights activists, hippie-dippy Experience (Danielle Mason) and self-righteous Grant (Oliver Driver), who drops a specimen jar. Out pops a mutated fetus that looks like a cross between “Alien’s” chest-buster and Lamb Chop the sock puppet. The critter promptly makes a meal of Grant’s right ear, and soon the virtuous vegan is sprouting woolly tufts and ripping the throats out of rabbits. That’s right: He’s a weresheep.

King doesn’t expect us to take any of this too seriously, but the movie is less a running gag than an ingenious prank. As if fulfilling the terms of an undisclosed bet, “Black Sheep” sets out to prove that the response to horror-film grammar is so ingrained that the right combination of signals can set our hearts racing even as our minds giggle.

The cast, including Tammy Davis as a handyman and Glenis Levestam as a housekeeper with a taste for innards, hits its marks flawlessly, even when the material isn’t first-rate.

Like “Shaun of the Dead,” “Black Sheep” is at once exhilarating and self-deprecating, knowledgeable without being fannish, clever but not too clever.

“Black Sheep.” MPAA rating: unrated. Running time: 1 hour, 27 minutes. Laemmle’s Sunset 5, 8000 Sunset Blvd. (323) 848-3500; Landmark’s NuWilshire, 1314 Wilshire Blvd. (at Euclid Street), Santa Monica, (310) 281-8223; and Regency South Coast Village 3, 1561 W. Sunflower Ave., Santa Ana, (714) 557-5701.