A pet ball which is formed from two (2) hollow semi-spherical half members and which is readily mobile along a hard surface, for example the ground. A weight, for example, a fishing sinker, is suspended within the pet ball. The weight is suspended by an elastic member, for example, an elastic rubber band, which is attached to the inside wall of the pet ball. The weight can be attached to the elastic member in such a manner that it can move along the elastic member or it can be fixed at a stationary position along the elastic member to create different desired effects. When a force is applied to the pet ball, it will roll. With the weight being suspended from the elastic member, the center of gravity of the pet ball changes as the pet ball rolls, thus resulting in erratic movement or a path which follows no definite or consistent direction or pattern. Each of the hollow semi-spherical half members include a hook member extending inwardly from their inside walls for anchoring the elastic member, which is attached to each hook member to normally retain the two (2) hollow semi-spherical half members together in a spherical ball configuration, but permits the two (2) hollow semi-spherical half members to be pulled apart or separated.