It’s hard to believe that New Line offered sneak previews of this movie as a special Mother’s Day treat. “Monster-in-Law” certainly offers one of the most unflattering portraits of a mother/ prospective mother-in-law ever to appear on film (which is really saying a lot), and any son or daughter who took his or her mom to it would have discovered that if it’s intended as a cheer to motherhood, it’s certainly one of the Bronx variety. Strident and unvaried, this one-joke farce is as silly and lazy as any third-rate sitcom.

Neither set-up nor follow-through offers any surprises. Charlie Cantilini (Jennifer Lopez) is a sweet, beautiful, hardworking young woman (she juggles no fewer than three jobs, as receptionist, waitress and dog-walker, though she wants to be a designer) who meets, in the customarily cute fashion, a flawless catch–a handsome, extravagantly thoughtful surgeon named Kevin Fields (Michael Vartan). Unfortunately, he has a prima donna of a mother, Viola Fields (Jane Fonda), a famous but recently-fired TV interviewer (just think Barbara Walters without the lisp) who’s also an extremely possessive parent determined to wreck the couple’s sudden engagement. When trying to embarrass middle-class Charlie at posh gatherings of her world-famous friends and encouraging a high-society type to seduce her son fail to achieve her purpose, she goes so far as to feign psychosis and thereby drive the prospective bride to distraction in order to derail the planned nuptials. After Charlie finds out what Viola’s up to, she retaliates with some mischief of her own. Of course the two eventually bury the hatchet at the ceremony, when a visit from Viola’s one-time mother-in-law (Elaine Stritch) makes Viola realize what a harridan she’s become herself.

One can imagine a movie like “Monster-in-Law” being made with wit and subtlety, but here it’s frantic slapstick and blunt force comic trauma that rule. Fonda, in particular, is encouraged by director Robert Luketic (who already showed his heavy hand in “Legally Blonde”) to mug and camp it up so ferociously as this mommie dearest that it’s almost as though she’s managed to combine, in a single turn, all the excesses that both Dustin Hoffman and Barbra Streisand brought to “Meet the Fockers.” And when she’s compelled to turn all teary-eyed and repentant at the close, the result is even more embarrassing. But contrast Lopez is positively lightweight as the put-upon Charlie; even after the worm turns, the poor thing can’t muster much more than an impish show of glee (and it’s still a worm, after all). But if the female match is rather unequal, the male side of the triangle is absurdly weak. Kevin is a dull, empty figure, totally oblivious to the machinations of his mother, and he’s played with such utter blandness by Vartan that a mannequin could easily have been substituted in the part without serious loss. And though the leading trio offer few nuances, the supporting characters actually exceed them in one-dimensionality. On Viola’s side we have Ruby (Wanda Sykes), a brash, sharp-tongued African-American aide who’s constantly spouting snide remarks about her boss’s antics. (Wanda is also employed, in a fashion that marks clumsy scriptwriting, to tell the audience how it’s supposed to react; so when Charlie finally tells off Viola toward the close, the eavesdropping Wanda can tell us, “That girl really knows how to give a speech,” as if we were too dense to recognize the fact.) As a balance, Charlie is given as a best friend the obligatory gay neighbor, thankfully played with less ostentation than one might have feared by Adam Scott. Stritch, on the other hand, provides little more than her patented acidic presence, and her big moment turns out to be astonishingly flat.

“Monster-in-Law” has the bright look Luketic seems to favor, thanks to Missy Stewart’s colorful production design, Kym Barrett’s costumes and Russell Carpenter’s spiffy cinematography, and it boasts a bubbly score by David Newman that accentuates every comic point as heavily as the director does. These elements, along with Fonda’s high-strung turn (especially after so long an absence from the screen), may well be enough to satisfy viewers conditioned by the ordinary run of network television to accept lowest-common-denominator comedy. Anybody who sets his sights higher, though, will find it a depressingly rote trip through extremely familiar territory.