One example of a toy system includes a first body, at least one accessory having an activation feature, at least one mechanism adapted to alter the first body, and a first sensor adapted to sense the activation feature and to activate selectively the at least one mechanism when the activation feature is sensed. The body may include first and second body elements that are moveable relative to each other, a drive element, and a sensor mounted relative to the body and adapted to be activated by a user. The second body element may also have a characteristic that is changeable. A first mechanism may have a plurality of operative states, and a function may be controlled based on the operating state.