She's got the deejay blasting Beyoncé and a computerized light show. She has nearly 100 friends crammed into Manhattan's ritzy Bryant Park Grill. She's got the gift table groaning with Tiffany bags and guests greeting her dad at the door with "Mazel tov!" Everything is perfectly poised for 13-year-old Kimya to have a world-class bat mitzvah, except for one tiny detail: Kimya isn't Jewish.

Welcome to the strange new world of faux mitzvahs, where non-Jewish teens like Kimya Zahedi—whose parents are Iranian-born Muslims—and Taylor Lasley, African-American and Presbyterian, get to party like it's 5764 (that's 2004 on the Hebrew calendar). A centuries-old Jewish tradition, bar mitzvahs (for boys) and bat mitzvahs (for girls) mark the passage from childhood to adulthood with rituals like candlelighting and slicing braided bread called challah, as well as with elaborate and often expensive celebrations. Now more and more non-Jewish kids are insisting on their own bar or bat mitzvah-style parties—without the religious rites and months of studious preparation—when they turn 13. "You see how you can have so much fun with so many people," says Kimya, who attends one or two bar or bat mitzvahs every weekend in and around her wealthy neighborhood in Alpine, N.J.

"We didn't want her to feel different from her friends," says her father, Tooraj, 46, a Manhattan endocrinologist. "A lot of my Jewish friends tell me they always wanted a Christmas tree and never got one. This is the same thing."

A phenomenon primarily in big cities and areas with large Jewish populations such as New York, Chicago and Los Angeles, faux mitzvahs are "starting to become popular and get buzz," says Marc Jason, whose Englewood, N.J., company Total Entertainment worked 12 such parties last year, compared to just a handful the year before. "It's contagious." For Kimya's Feb. 20 bash, the Zahedis shelled out around $40,000 for a caterer, deejay (her mom, Nassrin, 47, a cosmetic dentist, even asked him to play the hora), emcee and two professional dancers, a fog machine, a fashion show, a video montage of highlights from Kimya's life, and party favors from haut chocolatier Fauchon. The result was "no different from a bat mitzvah, just without the long service," says Kimya's classmate Andrea Yoss, 13, who had her bat mitzvah at Manhattan's Harvard Club in November. Adds friend Christina Guidera, 13: "The music was a lot better too. At bat mitzvahs they play weird songs for the parents."

But swiping the style of this Jewish custom and ignoring its substance just isn't kosher to some. "It's the frills without the faith," says Rabbi Jeffrey Sirkman of Larchmont, N.Y. "It sends the wrong message. The bar mitzvah is not only a grandiose affair; it's about an ongoing process of becoming a part of Israel." Yet Rabbi Irwin Kula, president of New York's CLAL—National Jewish Center for Learning and Leadership—welcomes the bar mitzvah's broader appeal. "In open societies people see each other's rituals and borrow them," he says. "You don't have to be Jewish to want a party."

That's exactly what inspired Taylor Lasley's "black mitzvah" last year. "I wanted to do something really fun that was in keeping with what the rest of my grade was doing at the time," says Lasley, who is African-American and a student at the Harvard-Westlake School in Los Angeles. "I asked myself, 'If my best friend is having a bat mitzvah, why can't I?' " Her parents, both real estate attorneys, agreed—as long as she kept the tab down to a superthrifty $1,000. (Among the ways Lasley cut costs: making her own invitations and serving turkey dogs and fries.) "We kept it low-budget," she says, "but it ended up being really good."

Clark Buden, the great-grandson of former Vice President Nelson Rockefeller, preferred his faux mitzvah to the many real deals he has attended because "I didn't have to sit there in a suit." Held in his family's private Tudor-style country club on the rambling grounds of the Rockefeller estate outside New York City, his December 2002 blowout featured disco lights pulsing on oil paintings of his famous ancestors, a diving contest in the club's indoor pool and phony money—with Clark's picture on it—for his 45 friends to bid on prizes at an auction. "Christians don't have a rite of passage like the bar mitzvah; it's something missing from our culture," says his stepfather Peter Humphrey, 57, a shamanistic healer (his mother, Clare Pierson, 47, is an herbalist). "Now kids get a car or driver's license as their rite of passage, and that's too bad."

Certainly the trend reflects the pressure on adolescents to keep up with their peers—and on parents to do their part. When Janie Bruyere asked her folks for a faux mitzvah, "I said no," recalls her father, Bob Bruyere, 52, who, like his wife, Anne Kniffen, 48, is a Dallas architect. But after Janie begged for three months, he gave in. Her Oscar-theme party for 100 friends in August 2002—featuring a magician, caricature artist, deejay and dance leader—was a big success. "I want our kids to be popular. I don't want them being the loner or the outcast," says Bruyere. "The party set Janie on the social list with all her buds, and she's been invited to every party since then."

For many parents, saying no is tough when "every week it's a new dress, a new outfit" for another friend's bar or bat mitzvah, explains Diana Beauchamp, a suburban Chicago playwright and mother of four, including two daughters who had faux mitzvahs (her husband, James, is a salesman for a high-tech firm). "I wanted them to feel it was just as important to us that she was turning 13 as it was to other parents." First, Antoinette enjoyed a $10,000 supermodel-theme shindig for 30 friends at Chicago's exclusive Metropolitan Club, complete with tattoo artist and ice-cream sundae bar in May 2001. Then in October 2002 it was her sister Renée's turn: 30 pals were ferried by limo and bus to a posh indoor botanical garden at Chicago's Navy Pier for an $11,000 Island Girl-theme affair. According to Renée, "some of my friends said it was the best party they'd been to."

And that's saying quite a lot. "Sometimes these girls go to several bar or bat mitzvahs in one weekend," observes Kimya Zahedi's cousin Hani Ahmadi, 22, as she watches her whoop it up on the fog-shrouded dance floor. "You can't just throw them a party at Chuck E. Cheese's."

Alex Tresniowski. Jennifer Frey in New York City, Wendy Grossman in Houston, Lyndon Stambler in Los Angeles and Anne E. Stein in Chicago