"Would you do it again?" I asked Rachel and Rosemary, who were some of the earliest risers at the American Museum of Natural History's first sleepover for grown-ups. They each paid $375 not only to sleep over, but to roam the halls during early morning hours, take part in flashlight tours and late night live animal presentations, sit down to a three-course meal, enjoy a champagne toast overlooking the Hayden Sphere Planetarium, and this morning: a continental breakfast.

"Yes," they both replied—but they wouldn't do it again right away, "maybe in another year." Rosemary was there to conquer her deep fear of the museum's giant blue whale, which terrified her as a child. Would sleeping directly under it in the middle of the night help? Nope. Panic set in, but Rosemary told me she pulled the covers over her head and tried to make the best of the situation. While she was there to face a childhood nightmare, most others in attendance were chasing childhood dreams.

About 150 people purchased tickets to sleep in the Hall of Ocean Life last night, though not everyone returned to their cots to catch some shut eye under the whale. The appeal of the event, after all, is being able to explore the museum's many corners... alone and in the middle of the night, like you're runaways Richie and Margot Tenenbaum.

As part of the small press pool attending, I was kept on a very tight leash, so it's hard to relay the authentic experience here. But I heard of things, those things that happen when it's late, your imagination switches to high gear, and even the babysitter has gone to sleep: a ghost on the third floor, a unicorn in the planetarium... and did you hear about the people with the flask of whiskey? Where are they? Probably having sex in the Power of Poison room.

While adventures like this were going on, I was brought to the Lunar Lounge. This was the space the museum set up for night owls, which provided a constant flow of old movies and cucumber water. Pillows on the floor and faux candlelight provided a Special vibe, but still not as special as those empty hallways. The place was vacant except for a passing few who needed an outlet to charge their phone. Instagram was an important part of this experience.

Those who did sleep did so mostly quietly. A creak here, a snore there... the only thing that was really keeping anyone up was the cots. Pretty sure they were not meant for adults, not even your worst enemy. But that makes sense—the museum has previously only offered sleepovers to children, and last night was a bit of a trial to see if the 21+ crowd could swing it. While everyone seemed on good behavior, it's unclear at press time what was caught on all those security cameras.

This morning, however, Media Relations manager Michael Walker told me, "I think we can safely say last night’s event was a success, so yes, I’m betting you’ll be seeing more grown-up sleepovers at AMNH." And when that happens, you should go. Go well-rested, and stay up all night—you're not going to want to sleep through this.