What about a bed that perfectly fits into a nook in the room, meaning that part of the room is nothing but bed with only one side open? Sized exactly so nothing sticks out either
In my house sharing days I actually applied to rent a room that was twin bed sized. It had storage shelves near the ceiling, which was fine because you had to stand on the bed to move around anyway. Somebody else got it and I ended up renting a corner of a finished attic (with skylights!!) along with 4 other people. I put up tapestries to section it off one night while my one of my attic mates was banging some dude she brought home from a party.
Sounds a bit of pain for two people if one side is the free one. Sounds a bit of a pain for both if it's the end that's open. Sounds like utter madness if it's the end with the pillows that's open, but insane enough to earn my respect.
I want that arrangement with the opening along the foot of the bed. But I imagine as a child this would terrify me, having no other possible escape route but through when the zombie shows up.