The smiling puppet descends the plane in a uniform motion. It turns itself upside down cutting capers.

Inside the puppet there's a sphere whose mass has been chosen so that it will remain in the superior part of the puppet in the instant of the overturn. Moreover, the little puppet's hands are collocated in an asymmetric way with respect to its axis, i.e. in a way that if we place the puppet on the stairs vertically, a non equilibrated moment of forces is generated by a couple of forces: the weight applied in the bary-centre and the reaction in the point.

Anyway, to make the puppet discend the stairs, we have to place it with the right inclination angle...

This toy shows us how gravitational potential energy gets converted into kinetic energy and into work against the friction forces. The motion is quasi-steady one, as it was in the case with the duck and elephant.

The secret of its design lies in a proper choice of the size of the puppet and the weight of the sphere so that at the instant of overturn the sphere would remain inside the upper part of the puppet. In addition the 'arms' of the puppet are asymmetric to its axis so that when we place the puppet vertically on the stairs, a non equilibrated moment of forces is generated by a couple of forces: the weight of the puppet and the reaction force at the fulcrum.

Yet, another essential construction aspect of the toy is a proper choice of the angle at which the stairs are sloping. By lowering the slope we can find the angle at which the puppet will not descend any more. That means that the increase of the kinetic energy in one pace is insufficient to compensate for the work against friction forces.