Kids are wired to be curious, and if they are engaged in play of their own doing (their own rules) they just love it and have fun with it. Sometimes toys (and even expensive toys) feed nothing into imagination and playfulness of kids. They are only one thing, but everyday common things like cardboard boxes, box of old clothes or kitchen utensils is a mine of ideas, and stimulates the creativity in children. It represents endless possibilities for them.
Those objects can become boats, cars, beds for dolls, TVs, aliens, Heroes…anything they like them to be. It allows their creativity to go wild. They can build whatever their hearts desire, using their own imaginations. They make up games and scenarios that they play out. It’s about having the freedom and autonomy to pursue their interests.
Playing with open ended toys likes boxes or rolls, etc… help build creativity, imagination and resourcefulness, which toys with more bells and whistles sometimes can't. It is important to provide the tools for playful learning than just toys.
In one such experiment, Preschool replaced toys with cardboard boxes, kids love it
Some ideas for playing with a box: