Before LEGO Mindstorms existed, LEGO created a set called "Robot" in an attempt to cash-in on the Transformers craze with this model which changed from a car to a robot, and back again. Unfortunately, I never had the set. Nor did I have the necessary pieces to build it. But, armed with the official instructions (and a 3D printer!) I did the best I could.
Marquis de Geek