  We describe the physics of an articulated toy with an internal source of
energy provided by a spiral spring. The toy is a funny low cost kangaroo which
jumps and rotates. The study consists of a mechanical and a thermodynamical
analysis which makes use of the Newton and center of mass equations, the
rotational equations and the first law of thermodynamics. This amazing toy
provides a nice demonstrative example how new physics insights can be brought
about when links with thermodynamics are established in the study of mechanical
systems.
