Toy sales in the US have steadily dropped for the past few years. But for more than a decade, the bright spot in an otherwise gloomy market has been toys aimed at grown-ups. In 2007, retail sales of playthings geared to the over-18 set were up nearly 10 percent.

“This is definitely one of the industry’s biggest trends,” says Gareb Shamus, New York publisher of the industry magazine Toy Wishes. “And it’s only going to increase as this demographic gets older.”

Whether it’s the Los Angeles rock musician who owns thousands of dollars of “Star Wars” action figures and costumes, a Dutch physiology professor with a basement full of LEGOS, or a Washington State chef with storage units and glass bookcases jammed with Muppet toys, this is a trend that grew from the era of mass-market tie-ins.