As Yume Nikki is a game about dreams, beds obviously have an important role in Madotsuki's life.
The most significant of these is the bed in Madotsuki's Room. Climbing into bed produces a three-second countdown while Madotsuki falls asleep, after which she will appear on her balcony in the dream world.
Dream World Beds
There are numerous beds within the dream world itself, some found in the most inexplicable places. There are five that can be entered initially, located in:
There are, in total, 71 beds in the Bed Room, however most are either occupied or unreachable. Only one can be entered - the center bed on the 5th row.
Any one of the five available beds may send Madotsuki to the Staircase of Hands when she sleeps in them, while the others will do nothing. The bed selected to do this is randomly chosen when Madotsuki falls asleep.
If she does not continue towards the Spaceship and instead takes Underground World's elevator up to The Mall, then she will be unable to return as it is one-way.
The Spaceship
In addition to the beds listed above, there is also a unique bed on the Spaceship. Unlike others in the dream world, it will not send you to the Staircase of Hands, but instead has a 1/6 chance of causing the Spaceship Crash event.
The Spaceship cannot be reached without first dousing the flames at the end of Underground World, which themselves cannot be reached without first falling asleep in the random bed listed above. This means that in order to access Mars, Madotsuki must fall asleep three times in three different beds.