Cami, an eighth grader, considers the hidden room the best thing about her family’s five-month-old French colonial-style house in this Chicago suburb. “When I heard that I could have a secret room, it sounded like so much fun,” she said, noting that the room initially conjured images of secret passages from Scooby-Doo cartoons. “My parents told me, ‘You could just put curtains over the doorway,’ but that wasn’t nearly as cool.”