Dancer-in-a-Box is a project to create a self-propelled cardboard box without an external drive system such as a wheel or propeller. Since the dawn of time, humans have used a box as a static object to store and transport everyday things easily. Therefore, we began to seek a new usage of the box as an active object. Based on this concept, we developed a self-rolling robotic cube which can be installed in a cardboard box. Also, this research created several applications using our robotic cube for entertainment purposes.