Dr. Jekyll and Jim Carrey

In the new Jim Carrey farce, Me, Myself & Irene, the rubber-faced comedian plays a meek Rhode Island state trooper named Charlie, whose aggressions are so pent up that they finally have to break out in the form of a second personality called Hank. Where Charlie silently endures potty-mouthed curses from little girls skipping rope, Hank swipes ice cream cones from kids at county fairs. Where sweet Charlie nibbles health food and tips his cap to young mothers in the supermarket, bullying Hank swills rum, gushes testosterone and threatens unsuspecting strangers in withering Dirty Harry tones. Charlie's a shlub. Hank's a menace. And here's news: The dual role gives Carrey all kinds of room to do his trademark shtick. He speaks in tongues, twists his features into unimaginable shapes and tears up cars with his bare hands. He alternately woos his leading lady (Carrey's off-screen girl, Katy native Renée Zellweger) with sweet nothings and blasts her with raunchy misogynistic insults. He even gets into an extended fistfight with himself.

Jekyll and Hyde never had it so good. Neither did the wimpy bank-clerk-turned-swaggering-superstud Carrey created in The Mask.

Here the manic comic's partners in crime are his old pals the Farrelly brothers, Bobby and Peter, who have previously disturbed the peace with such in-your-face comedies as There's Something About Mary and the Carrey-Jeff Daniels vehicle Dumb and Dumber, which grossed an astonishing $340 million worldwide. Intimates of the Farrelly oeuvre have come to expect some major outrage to go with their yuks, and the brothers are notoriously eager to comply.

In Irene, a barnyard chicken gets stuffed into the hairy butt of a cop. Charlie empties his pistol into a fallen cow at roadside. There's an albino psychopath named Whitey (Michael Bowman) who says he murdered his entire family. A surly black midget with a genius IQ (Tony Cox) beds the hero's wife, who then gives birth to triplets. Let's not even get into the bodily function jokes -- or the business of the giant dildo.

Carrey and the Farrellys are equal-opportunity offenders, to be sure, but so far the only group to get its hackles up has been the National Alliance for the Mentally Ill, which has protested the movie's "gross ignorance and insensitivity to people with mental illnesses and their families." NAMI's main complaint is that Charlie/Hank is repeatedly called a schizophrenic or a schizo. Actually, schizophrenia is a severe, biologically based brain disorder whose hallmarks are auditory hallucinations, or imagined "voices," and a variety of serious thinking and perceptual glitches. It's certainly no joke. And contrary to popular misconception, schizophrenia is not multiple personality disorder. NAMI is understandably upset that another Hollywood movie is perpetuating that myth.

On the other hand, a Jim Carrey comedy is not exactly graduate school, and if the Farrelly brothers feel like throwing elements of The Three Faces of Eve and The Nutty Professor into their comic pot, the most serious charge you can level against them is petty theft. Carrey has been compared to Jerry Lewis for years, and if Hank isn't a soul brother to Buddy Love, the narcissistic alter ego Lewis played in Professor, he's the closest thing to it, right down to his contempt for Charlie's bashfulness. "Charlie's like origami," obnoxious Hank seethes. "He folds under pressure."

Jim Carrey never does. After his forays into more "serious" work like The Truman Show and the Andy Kaufman biopic Man on the Moon, the Canadian-born dynamo looks perfectly at home in Irene as Charlie/Hank relieves himself on his rude neighbor's lawn or wheezes a little symphony through a broken nose. If there's nobility in sheer silliness, Carrey manages to tap into it. Meanwhile, the Farrellys, who wrote this script back in 1990 with an old Rhode Island friend, Mike Cerrone, and co-directed, also make way for Carrey's real-life lady love. As the feisty Irene, who's on the lam from thugs and crooked cops when she bumps into the ditsy state trooper, the petite Zellweger (who romanced Tom Cruise in Jerry Maguire) gives off appealing sweetness and heart. She's got some wiseass lines, too, but for the most part she's a welcome antidote to her boyfriend's relentless energies, which can be exhausting even for the audience.

Okay. Cards on the table: I admit to a weakness for Carrey's most puerile high jinks, and for the go-to-hell bad taste of the Farrelly brothers, which is a hit-and-miss endeavor at best. Their brazen crudeness awakens the inner six-year-old in many of us -- like playing Chinese checkers once in a while or eating corn dogs at the drive-in. Those are not necessarily bad things, unless there's no inner 30- or 46-year-old to carry the freight the rest of the time. Most grown-ups come equipped with that, of course; in the case of this actor and these moviemakers, the jury is certainly still out. So much the better.