Amazing how a plain old cardboard box and the wonderful imagination of a child can take them to places far and beyond! The moment our 4 years old boy got into the cardboard box (we have quite a number of these boxes at home) he started doodling and drawing steering wheels, buttons to press all around to launch his spaceship-racing car-house or whatever he fancies the cardboard box to be at the moment.
I also make use of the opportunity to teach my kiddos to share and play together since we only let them have one cardboard box at a time, so they have to play nice and co-operate together.
I also get to rest a few minutes while they both have a go at the cardboard box hahaha... nice, nice...