The object of the present invention is a device by means of which simulation of the lengthening of shortening of, for example, a limb is obtaining by construction of a telescoping structure, the mutual sliding of which, and therefore the lengthening or shortening is controlled by means of threads that are rolled or unrolled from a disk shaped like one or more side-by-side pulleys. Thanks also to the action of a counteracting spring. The movement of the spools is controlled by a circuit that registers shaking and therefore playing with the toy according to the equation, more playing=more growth (that is, more shaking more growth).