At 25, Stephen Brown thought his toy-playing days were over—until his mom tried to clean out his old bedroom. "Looking at my 'Star Wars' guys, I couldn't pull the trigger," says the Atlanta advertising executive, now 34. Over the next decade, he spent more than $5,000 on a Pac-Man lunchbox, a Mr. T Chia Pet and enough childhood tchotchkes to fill a man-size closet. But Brown isn't a collector. "These are for play, not profit," he says. It's a mentality shared by a growing number of Gen X- and Yers: they want their stuff back, whatever the cost. "I'm taking a bath," says Chris Anderson, a 40-year-old Dallas marketing manager, who spent $1,000 on games like Mattel's 1977 handheld Electronic Football. Tom Miano, owner of Serious Toyz in Cold Spring, N.Y., recently sold a box of 30 scuffed He-Man figures for $330, despite missing weapons and limbs. At $15 to $30 for each action figure, re-staffing the Cobra Command center (home to G.I. Joe's arch-nemesis, Cobra Commander) isn't cheap. So what's driving this rejuvenile movement? Marketing, mostly. Toys from the 1970s and '80s came with unprecedented tie-ins, enclosing their youthful fans in a complete universe of bedspreads, backpacks and lunchboxes, not to mention theme songs that echo through the decades. "They create immediate connective tissue," says Brown. It takes a big boy to admit that.