No matter that wee sweats cost $100 and eency dresses fetch twice that. Parents in 35 countries—and now, belatedly, the U.S.—have found it impossible to resist the kaleidoscopic hues and textured fabrics of children's clothes from the Dutch label OILILY. (The name rhymes with Boy Billy.)

The appeal is "a wonderful combination of colors and prints," says Cosby Show costumer Sarah Lemire, who has put Huxtable cuties Keshia Knight Pulliam and Raven Symoné in Oilily dillies. When textile engineer Willem Olsthoorn, 51, and his wife, Marieke, 49, a designer, founded the label 26 years ago, however, the world wasn't ready for their chromatic capers. "Baby clothes were pink and blue, and we made completely different colors," recalls Willem. "People slapped their knees laughing. At the end of the '60s, we had just 15 items in our line."

With 200 employees now turning out 200 styles and projected sales of $90 million by next year, the Olsthoorns got the last giggle. Indeed they have established a legal department to stop plagiarists. Increasing amounts of their revenue are coming from their new U.S. boutiques after a failed department-store foray in the early '80s. Oilily—a spin on his nickname, Oily—is now thriving in Southampton, N.Y., Boston, Chicago and Aspen, with more franchises planned in Beverly Hills and Washington, D.C., by fall.

Parents of four, including identical twin girls now 23, the Olsthoorns dismiss the prevailing notion that tykes should dress like miniadults. Instead their designers create whimsical, pull-on pieces meant to mix any which way and be worn to school, parties or—for the truly extravagant—the playground.

About 16,000 fan letters a year testify that "children are establishing their own sense of style," says Willem. And spreading it. Oilily launched a women's line a few years back after moms started scarfing up large girls' sizes. Last December, after stocking up on pants, skirts and sweats for daughter Alexa Ray Joel in the Aspen outlet, Christie Brinkley couldn't help indulging in a few adult-size jerseys for herself.