In this paper we describe the outcomes from a design exercise in which eight groups of designers designed and built hardware sketches in the form of playful shape-changing prototypes, generatively working with Rasmussen et al's [31] eight unique types of shape change. Seeing that shape-changing interfaces is a growing area in HCI design research and that authors often shy away from articulating the special qualities brought to a design by using changing shape to communicate information, we set out to explore shape changing interfaces through a series of sketching experiments through the support of Danish toy company. Eight design groups redesigned existing tumbling objects for children using electronic sensors and actuators guided only by the request to adhere to the client's design goal to inspire imagination and movement in users. The main contributions of the paper include indications for the further expansion of the design space of shape changing interfaces relating to the perception and understanding of behaviour, causality and the mechanics involved in shape change events, which we call "Imagined Physics." This concept is described along with additional insights into the qualities of shape changing interfaces coined in recent research in the field.