Children can turn anything into something fun to play with.
To an outsider it may appear to be just a ready to collapse pile of cushions and blocks, but to the child it is their impregnable fortress. When I first learned about the topic I knew I had to use a sofa fort and a set of block I remember from when I was growing up. My first draft was to just have those two things in a living room setting. My next idea, after I came up with the teddy bear, was to have the bear inside the cushion fort with some sort of invasion force, tanks or robots, closing in. I tinkered around with the invasion force idea for a while.