Some childhood fantasies age poorly, the charms of space travel or magician’s school fading with time. An evening at the museum need not be among these.

The doors close for the day, so goes the dream, but a fortunate few are left behind, dwelling among dinosaurs and dioramas, stargazing in the planetarium while the city sleeps. Will the exhibits behave themselves after hours? (Hollywood suggests otherwise.)

The American Museum of Natural History in Manhattan has offered sleepovers for families since 2006.

But this time was different. On Friday, the museum held its first adults-only sleepover. No one under 21 admitted. Visitors paid $375 to attend, with a modest discount for members ($325). The event sold out in three hours.

Beginning at 6:30 p.m., about 150 people — encouraged to haul pillows, toothbrushes and “comfortable sleeping attire” (cots to be provided) — were essentially given the run of the place. They received a three-course dinner and snacks, with alcoholic drinks included. Organized programs highlighted poisons and sharks, among other foreboding topics. Many set out on their own.