Back in 2009, when Brooklyn-based dancer Jessica Williams taught a friend, her fiancee, and their bridal party an exuberant Bollywood-style dance number for their wedding reception, the response was overwhelming.

"Everyone went so nuts for this dance - people were standing up, taking pictures and video-recording it. And then, after it was all said and done, everyone wanted to do it again," Williams said. "I was leading dances for the rest of the night - and that's when a lightbulb went off in my head, that there's a huge need for this."

So, POP n' wedLOCK - based in New York and Philadelphia - was born.

Williams and Karmen Fails of West Philadelphia, both 29, launched the company in February to tap into an explosion of interest in choreographed dance numbers that turn the traditional first wedding dance on its ear. While couples have long taken lessons so their first fox-trot is flawless, the ante has been upped: From groomsmen executing a perfect rendition of Michael Jackson's "Thriller" video to father-daughter dances that switch on a dime from the waltz to the Soulja Boy, newlyweds across the region and beyond are using dance to inject fun, personality, and individuality into their weddings.

Fails said couples in their 20s and 30s, who grew up on music videos and are comfortable with reality shows such as TLC's Rock the Reception, a 2008 series devoted to unconventional wedding dances, want to offer their guests an event that's unique and unforgettable.

"As our generation progresses, we become more liberated in our expression," she said. "We hold onto certain traditional values, like getting married, but as far as how it comes together, we always want something a little different for ourselves."

For one couple, Fails created a dance that incorporated "hip-hop moves, jazz, and a little Fred Astaire and Ginger Rogers," to a song by R&B singer Chris Brown. For other clients, the dance lessons have doubled as bridal shower activities, allowing the entire bridal party to learn moves to perform at the reception.

While some dances are taught on the spot the day of the wedding, more elaborate performances may require five or more lessons, Fails said. Choreography and training starts at $100 - which would cover two lessons for a couple - and increases based on the size of the group and the complexity of the dance.

POP n' wedLOCK clients Lauretta Gooden, 39, and Jamarr Kellan, 37, of West Philadelphia are planning to wow the guests at their June wedding with two dances. First, Gooden will perform a burlesque number for her husband; then, he'll join her in a hip-hop dance. Since both are part-time performers (Kellan was once a backup dancer for various rap artists), Gooden said it just made sense to inject homegrown entertainment into the potluck reception they're planning at their home for about 50 guests.

"We wanted our wedding to be nontraditional, and to do something special for our guests," said Gooden.

Part of the fun, said Gooden, is that none of the guests will be expecting it.

After all, it's no longer enough merely to impress wedding guests: Some couples now want to shock them.

That's true for Brandon Rogers and Bella Udofa, both 29, of Columbus, Ohio. For their July wedding, they commissioned POP n' wedLOCK to create a surprise dance-off that starts with a fictitious tiff in the middle of the mother-son dance and concludes with an energetic group hip-hop performance. Because the teachers were a state away from the students, Fails and Williams videotaped a step-by-step guide for each participant's role; Rogers expects to spend about 15 hours per week rehearsing in the run-up to his wedding.

"Everyone has a first dance, and everyone cuts the cake, but after the wedding what are you going to remember?" Rogers said. "We feel that we'll make an unforgettable moment that everyone will be talking about forever. . . . You're not going to forget the crazy dance that we did - and everyone is going to tell all their friends."

And, if all goes well, Rogers intends to put the video online. "If we're pretty awesome, then I'm going to show the world," he said.

The prospect of viral video stardom motivates many, inspired in part by Minnesota couple Jill Peterson and Kevin Heinz, whose wacky, free-form 2009 processional dance, which had the groom somersaulting down the aisle, has garnered nearly 66 million YouTube hits.

Matt Ostroff, a manager at the Philadelphia event planning and entertainment company EBE, estimates that 5 percent to 10 percent of his clientele are now opting for unusual or surprise dances, either creating their own choreography or contracting an EBE choreographer to design a dance for them. Pricing can vary, but typically those services would cost $250 to $1,000, said Ostroff.

"We've definitely seen an increased demand for it. We have one coming up that's really cool, where we're bringing in a whole flash mob," Ostroff said. In the middle of the couple's first dance, 100 people who are not guests will show up with a surprise choreographed routine.

Ostroff said it's a logical extension of the current trend.

"I think that the whole bridal party or the family doing the dance has almost become commonplace over the past couple of years," he said. "These folks were simply looking for something that hasn't been done yet."

Alicia and Billy Leahy, both 28, of Ardmore, were also inspired by the nationwide resurgence of dance fueled by TV shows such as Dancing With the Stars.

For their wedding last September, Alicia Leahy, who teaches at Touch of Class Dance Studio, choreographed a surprise performance for the couple and their 16-member bridal party, to a medley of classic hip-hop songs.

"We've been to a wedding where the bride and groom did something, but [my husband] thought it would be cool to have everyone do it together," she said. "My maid of honor was eight months pregnant doing this dance. Everybody loved it."

Rogers said many weddings today are as much about entertaining guests as they are about the couple's future together. "When it came down to it, we wanted a huge show," he said.

He pointed out that a city hall wedding or a 400-person fete have the same outcome: marriage. "But the big wedding is a production. What's the point in spending money and time on something no one will remember?" he said. "Hopefully, 20 years down the line, people will say, 'I remember when you broke out that dance. That was crazy!' "