What did you do for fun this weekend?

Perhaps you drove your Beetle or big shiny truck to the multiplex to see that pirate movie (very similar to one you'd seen before), or maybe the one about a crime-fighter who flies through the air wearing a cape and tights.

On the way, maybe you treated yourself to a chocolate-flavored frozen coffee drink and took a call on your pink RAZR phone, whose ringtone is the theme song from your favorite retro TV show. Maybe you were wearing an oversize T-shirt, baggy shorts and slippers, or some similar get-up that wouldn't be out of place in a middle-school cafeteria line.

If this describes you, it describes millions of other Americans, too — something new in history, a variety of adult whose consumer tastes, favorite pastimes and even living arrangements smack distinctly of, well, childhood.

At home and in the workplace, at the shopping mall and in pop culture, it sometimes seems the whole grown-up population is going through a major regressive episode.

A smart new book, Christopher Noxon's "Rejuvenile: Kickball, Cartoons, Cupcakes, and the Reinvention of the American Grown-Up" (Crown, $23.95) confirms these suspicions, placing today's overgrown children in a historical and economic context, giving us a framework for thinking about the trend.

"People all over are refusing to act their age," Noxon writes. And the book is full of anecdotes about middle-aged Little Mermaid addicts, twentysomethings who attend overnight pajama parties and men who spend $300 on high-tech pogo sticks. He amply makes the case that from Cirque du Soleil (it used to be uncool to go to the circus after age 10) to comic-book movies to gourmet cupcakes, kid culture has invaded adult pursuits in a big way. Consider some of Noxon's stats: