(FORTUNE Small Business) – Fonzie's brown leather jacket from Happy Days. Barbara Eden's pink genie ensemble from I Dream of Jeannie. The Batman and Robin costumes. Alice's maid uniform from The Brady Bunch. Those famous '60s and '70s television costumes are housed under one roof, but not in a museum. They reside in the northern New Jersey home of John Azarian, 43, a commercial real estate developer. With 200 costumes and 300 props from the early years of color television, Azarian now has a collection he estimates to be worth more than $2 million.

He didn't pay $2 million for it, though. "When I started, there were few other collectors in this field," says Azarian. "People were more into movies or contemporary stuff. In the past four or five years that has changed, and prices have increased fivefold and tenfold on some pieces." Margaret Barrett, head of the popular-entertainment department at Christie's, has seen a rise in the number of collectors for these items, particularly among baby-boomers. "People get more sentimental the older they get," she says. "These items remind them of their youth." In November, Christie's sold a prop sink from The Honeymooners that it had estimated would fetch $5,000 to $6,000. Instead the sink went for $19,120.

Azarian's obsession started with Batman and Robin. In 1995 he found out that the only complete set of their costumes from the 1960s TV series was coming up for auction. "My jaw dropped, and I had to have them," says Azarian. His mom used to read him the words "Pow!" and "Bam!" from the fight scenes of the TV show before he could read them for himself. He bought the costumes through an auction house in California, and though Azarian won't say how much he paid for anything in his collection, he estimates the Batman and Robin costumes would be worth about $300,000 today. He also owns costumes from the supporting cast: Catwoman, Chief O'Hara, the Joker, the Penguin, and the Riddler.

Azarian's other prize is his Lost in Space collection. He has every major character's costume from all three seasons, including June Lockhart's green and pink bathrobe (bought directly from Lockhart) and the four-foot-wide model of the Jupiter 2 spaceship that was used in takeoff and landing scenes. When New Line Cinema released a film version of Lost in Space in 1998, it hired Azarian to display his collection at the press junkets. He also has Star Trek tunics from Captain Kirk and his crew.

Azarian's collecting philosophy is to buy only iconic costumes. "You should be able to look at them and say, 'Oh, my God! That's so and so,'" he says. "I don't collect stuff where I have to explain what it is." He owns one of two known Wonder Woman costumes, complete with boots, earrings, golden lasso, tiara, and bullet-deflecting bracelets (made from the rare metal "feminum").

Despite the value of his collection, Azarian has no plans to sell any of it. In fact, in ten years of buying he's sold only one piece: Ralph Kramden's bus driver jacket from The Honeymooners. "Someone contacted me who was a real obsessed fan," he says. "I said no, but he offered me such a ridiculous sum that I took it. I regret selling it now."

He stores most of the collection in a cedar closet with its own alarm system, and unless he's entertaining houseguests, Azarian keeps it out of sight. His greatest enjoyment of this unusual hobby, he says, comes from "just knowing I have a piece of television history in the closet."