Sleeping with the dinosaurs

It's possible that a few children here have read "From the Mixed-Up Files of Mrs. Basil E. Frankweiler," that 1967 E.L. Konigsburg classic tale of stowing away in the expansive marble confines of a museum. Let me tell you, the actual experience of sleeping in a museum is better than any childhood fantasy – even for an adult.

Tonight, the grandfather of natural science museums is relaunching its first sleepover program since 1988. Once the doors have closed to the public and the last visitor has been ushered out, 250 guests will remain behind to spend a night in this sprawling institution overlooking Central Park. At night, the American Museum of Natural History is exquisite.

Of course, this Sunday evening has none of the erudite rebelliousness of running away to test one's tiny mettle in the greatest of educational spaces. No, this slumber party is sanctioned. But little urban campers – and their fortunate chaperones – will still get a chance to peer behind the curtain.

Tonight's event is the first of many at the museum. The occasion also happens to be sharing billing and reception space with the world première of Ben Stiller's new comedy, "Night at the Museum," which was set here. Stiller plays a hapless nocturnal museum guard who discovers that the exhibits come to life.

Despite the red-carpet hoopla, many of tonight's visitors – children of museum employees, trustees, and other VIPs – profess to be more excited about the sleepover than the film. (Though moments after surveying the Hall of Ocean Life, where she'll "camp," an Ugg boot-clad gradeschooler tells a friend, "This is the coolest thing, ever – let's go find movie stars.")

Second graders David Kahana and Michael Bucca have come in from New Jersey. They are excited – and so are their fathers, who won the tickets at a charity auction. On the itinerary tonight is a flashlight tour of the dinosaur wing. David knows they have his favorite dinosaur there: a Triceratops.

"He just seems tough, with three horns coming out of his head," says David, touching his own small forehead. Michael likes the squid and the whale diorama, which isn't far from his cot (and was featured in last year's movie by that name). "They're fighting and that's cool," says Michael. "And when they're done fighting, the whale has scars."

I ask if they're worried that the 94-foot, 21,000-pound blue whale suspended above their heads may come to life in the night, like the exhibits in "Night at the Museum."

"It's going to be impossible," says David, giving me a look. "There's no water up there."

"Yeah," says Michael, looking up. "All there is, is air."

COSI, the science museum in Columbus, Ohio, is credited with being the first to open its doors at night, in 1972. Since then, many other natural history and science museums have followed suit – with a handful revamping their programs in time for the movie. Children's and living history museums also offer overnight experiences. And zoos and aquariums take advantage of the opportunity to spotlight nocturnal animals.

After escorting their children through the madness of a red-carpet, hallways, grand staircases, and into this 29,000-square-foot hall, parents unfurl sleeping bags and plump pillows. The settling-in process, which begins at 5 p.m., takes hours. Blame Ben Stiller. Before anyone can begin a flashlight tour of dinosaur fossils or an after-hours excursion into the live amphibian and reptile display, Stiller makes an announced "surprise" pass through the sleepover room and screens his movie.

Finally, at 10:30 p.m., after the well-received screening and star-studded reception, sleepover guests are separated from the black-tie Hollywood crowd and summoned back to the Hall of Ocean Life, where the lights have been dimmed. The effect is magical. Iridescent blue "skylights" fill the room with what looks like a glowing bioluminescence. Shadows ripple across their surfaces and dance over the arching blue whale. It gives new meaning to the idea of sleeping under the stars.

But it's not bedtime. Instead, the group files into the dinosaur gallery. The room is completely dark save for a flashing strobe and wild beams coming out of the flashlights the children carry, which flicker over looming dinosaur skeletons – and faces.

Chris Raxworthy, a curator of herpetology at the museum, wears a headlamp. He says he's spent some late nights working here. One time, after missing the last train home, he had to stay over. "Sometimes you get that, you know, funny feeling," he says. "But what's special about tonight is being able to bring my children." Timothy and George are museum regulars.

Unfortunately, the exhibit on lizards and snakes is fully lit, making it hard to get any sense of nocturnal behavior. But even though it's well past his bedtime, "Dave," a water monitor lizard, decides to be a good sport. He wakes up, looks around, and flickers his long forked tongue. Dave has been up this late at least once before – he was a guest on Letterman.

On the elevator back, a father tells the other parents that the last time a friend did this sort of thing, the kids slept only one hour. They look stricken. But by 11:30 p.m., many of the children already are sacked out, tiny arms hanging over the sides of cots. Shortly after midnight – official lights out time – the background din has quieted to a hum. The coziness of sharing a room with hundreds of urban adventurers is palpable. It is as close to camping as seems possible in a big city.

At 6 a.m., a few lights come on. The room begins to feel like a classy gymnasium after a school dance or a lock-in. Outside, the still darkened city is coming to life, oblivious to the great adventures that took place in here overnight. Groggy children submit to parents who help them out of flannel pajamas and into school uniforms. It's a Monday, after all. Others sneak a few extra minutes of sleep as bags are packed and sleeping bags stuffed.

Two boys exit with a flourish: They walk from the direction of the squid and whale diorama, pausing directly beneath the colossal blue whale to stage their own mini battle with the balloon light sabers that were made for them the night before.

Clifford Augustus has worked at Chicago's Field Museum for 23 years. In that time he's helped keep watch over its 20 million specimens during days, evenings, and overnight. Mr. Augustus tells the story of a colleague who was making her rounds late one night when she heard a scream. "She was so freaked out, she didn't want to go into the exhibit to see where the scream came from." The next morning, one of the mummy cases was found shattered, and the jaw of the mummy had dropped open, leaving its mouth in the position of a scream. The cause, according to museum scientists, was a sudden change in temperature. "You try to rationalize it," says Mr. Augustus. "But some things are just unexplainable."

Museums with movie-themed sleepovers:

"A Night at the Museum," American Museum of Natural History, New York. Children ages 8 to 12. $79; includes snack and breakfast. 5:45 p.m. to 9 a.m. (www.amnh.org/sleepovers)

"Dozin' with the Dinos," The Field Museum, Chicago. Children ages 6 to 12. $47; includes snack and breakfast. 5:45 p.m. to 9 a.m. (www.fieldmuseum.org/calendarsystem/overnight.asp)

"Night at the Museum Camp-In," Omniplex Science Museum, Oklahoma City. Cost of $40 for students, with OmniDome movie, snack, and breakfast; $25 for adults. 6 p.m. to 8 a.m. (www.omniplex.org)