How J.Lo can you go?

Think back to the glory days of the early ‘00s. JenniferLopez was everywhere you turned: on the big screen with her latest film, on theradio with her latest club hit, in the cosmetics counters with her latestfragrance, and — ah, yes — in the tabloids with her latest escapades. Rememberwhen she traveled to England and supposedly demanded to have more security thanQueen Elizabeth? How about when Matt Damon allegedly warned buddy Ben Afflecknot to marry her because J.Lo was nothing more than a “serial bride”? Or thestories about how she held up a press junket for hours because she broke a nailon the way to an interview and she had to get an emergency manicure?

Whether she was the biggest star in the world or not, Lopezwas unarguably a media phenomenon — at least until the colossal flop of “Gigli”and her break-up with Affleck tarnished her luster. It’s been three years sinceshe last starred in a film (the box office bust “El Cantante,” with husbandMarc Anthony) and a lot longer than that since the Star and the NationalEnquirer were scrutinizing her every move and every utterance.

Sounds like Comeback Time. But instead of choosing a projectthat might showcase her dramatic skills (and, with all the attention paid toher personal life, it’s easy to forget Lopez can be a vibrant actress) Lopezhas opted instead for “The Back-Up Plan,” a puffball of a comedy that makes“Maid in Manhattan” and “Monster-in-Law” seem like meticulously craftedmasterpieces by comparison. Put it this way: If someone had presented Lopezwith a pile of 500 rejected screenplays and told her to reach in and pull outone at random, the odds are excellent it would have been superior to thisinsipid, all but unendurable fiasco. About the only service “Back-Up” does forits star is to show that she’s still luminous and limber at age 40, aftergiving birth to twins; beyond that, it does her no favors whatsoever.

Impeccably groomed and firm of figure, Lopez looksastonishing throughout. Unfortunately, Kate Angelo’s witless, brain-numbing screenplayshoehorns the star into one idiotic situation after another and forces her tospit out dialogue so wretched it belongs in a diaper, not on the pages of ascript.

Lopez plays Zoe, the glamorpuss owner of a Manhattan petstore in which her employees fawn over her and a crippled puppy is always onhand to supply kooky canine reaction shots to the supposedly zany antics thatgo on. Traumatized by the ticking of her biological clock and the absence ofany potential boyfriends, Zoe decides artificial insemination is her bestoption. As fate would have it, minutes after leaving the sperm bank, Zoeliterally bumps up against Stan (Alex O’Loughlin), who has “baby daddy” writtenall over him. He’s a dairy farmer who makes and sells goat cheese at a swanky farmers’market, a job that enables him to say provocative things like “I’ll give you ataste of my cheese” with a straight face.

Zoe eventually tastes many things Stan has to offer, butwhen she tells him she’s in the family way, the revelation leaves a bad tastein his mouth. But instead of merely ending the relationship, Stan behaves likea capricious schoolgirl, alternately throwing tantrums and sweet-talking Zoe.She wants a baby and he acts like a baby, so the movie assumes they must be aperfect match.

More make-ups and misunderstandings follow, while Angelo anddirector Alan Poul shamelessly pile on every single overworked, unfunnystereotype they can get their grubby hands on. Tattooed, snarling lesbiansingle moms, wacky obstetricians who say “vagina” a little too often, blowsybest friends, salty-tongued senior citizens, and New Age loonies surround Zoeand Stan, although humor doesn’t come anywhere in their vicinity. About theonly thing that’s even smirk-worthy is Zoe’s rumination about the toll pregnancyhas taken on her physique: “I miss my old ass,” she wails in a J.Lo in-joke.“It was like this ass, but waaaay hotter!”

Lopez is often a laugh riot on talk shows and in interviews,but her comedic gifts are conspicuously absent here. So is any discernibletrace of chemistry with O’Loughlin, whose performance amounts to little morethan staring appreciatively at Lopez and taking off his shirt at appropriateintervals. One of the movie’s comic highlights involves Stan being accused ofbeing a potential pedophile by an over-protective parent (Anthony Anderson); nowonder O’Loughlin frequently looks and sounds terribly uncomfortable.

Soon after that awkward encounter, Stan and his accuserdiscuss the pros and cons of fatherhood. “It’s awful, awful, awful, awful,” thedowntrodden daddy says. “And then something wonderful happens.” “The Back-UpPlan” is exactly the same way — except for the “wonderful” part.