A decade ago, when Christine Johnston was a high-powered global brand manager at Pricewaterhouse-

Coopers and Martin Duffy was creative director at the Philly ad agency 160over90, they had little idea they would be spending their coming years wrangling unruly preschool-age boys on photo shoots.

"It's like working with drunk old men," Duffy joked.

But it's worth the hard work - and the occasional bribe - to capture perfect promotional images for the couple's Wonderboy Clothing line.

Now, they've added girls to the mix with the spring launch of 'Stun, a collection of halter dresses, blouses, shorts, and skirts sporting clean lines, vibrant hues, and bold graphic prints. The first collection, comprising 35 pieces in crisp cotton and casual knits, is debuting in about 70 boutiques, including Genes and Born Yesterday in Philadelphia.

The couple began contemplating design as a family business back in 2001, when Johnston left the corporate world to start a family and launch her graphic design firm, Johnston Duffy.

"I really wanted to get back to the basics of design," Johnston, 44, said.

After the two had their son Calder, now 7 - named, aptly, for the sculptor Alexander Calder - Duffy, 45, joined her at their home office in Queen Village. The couple quickly picked up clients ranging from locals such as Wawa and Tbar teahouse to national accounts such as CoverGirl and Swatch Group. But by 2004, Johnston was on the move again.

"I wanted to create a product," she said. "I love textiles, and I love creating prints and patterns. And, having a son, I noticed that [boys' clothing] was an underdeveloped market. So, I just took a shot at it."

Six months after she formulated the idea, Johnston was shipping the first collection to Barneys and a number of children's boutiques. Now, she sells 5,000 to 10,000 pieces each season for boys ages 6 months to 10 years at more than 120 stores globally.

After establishing the brand with 11 seasons of boys' wear, Johnston decided to launch 'Stun (short for Johnston), for girls ages 2 to 10.

Now, Johnston designs the clothing collections while Duffy helms the graphic design business and creates marketing materials, graphic T-shirts, and tags for Wonderboy and 'Stun.

"But it's a collaboration throughout," Johnston said. "We are a design-loving family."

That collaboration is evident in both lines, which reflect inspirations from vintage textiles, graphic design archives, and even Asbury Park's smiling icon Tillie - in short, from anywhere but the children's department.

Wonderboy's first collection of dress shirts in mod prints and sophisticated color palettes was unlike anything on the market. At that time, "all you could find were rocket ships and footballs," Duffy said.

Johnston's designs have more in common with grown-up attire, which is partly why the lines, priced from $25 to $125, are so popular with design-savvy parents and grandparents. "Parents tend to want to dress their children similar to how they dress themselves, and that's definitely a trend within the past 10 years," Duffy said. "They look at the children as an extension of themselves."

That appears to be especially true among the line's celebrity clientele, including Will Smith, Kelly Ripa, Mary Louise Parker, Melissa Rivers, and Alison Sweeney, who all have been photographed with their Wonderboy-clad sons.

Kristina Ferrari, owner of Genes children's boutiques in Wayne and Northern Liberties, finds that parents adore Wonderboy because of its cool aesthetic and detailed tailoring.

"Whenever dads come in, they always say they want the shirts for themselves, too," Ferrari said. "It's a great way to make children's clothes not be something less than adult clothes. There's as much attention to detail as there would in a perfectly tailored men's shirt - it's just that it happens to be for a child."

It's become so trendy that clients are sometimes surprised to learn of the company's Philadelphia roots.

Every facet of production takes place in the greater Philadelphia area, from manufacturing the fabrics and knits to pattern-making, screen-printing, and sewing.

That local focus has inspired other projects, like Bolt44.com, an online fabric clearinghouse Johnston started with the hope of selling to independent craftspeople.

Next up, the couple is considering entering the tween and teen clothing market. But in the meantime, they've finally moved out of that crowded home office into two chic postindustrial studios a few blocks from each other - one in Fishtown and one in Port Richmond.

As for the future, Johnston said, "I'm one of those people who doesn't like to sit still - I always want another project. Martin says, 'Don't start another business, not this year!' But it's anyone's guess." I

Samantha Melamed is a freelance writer based in Philadelphia.