A toy that can be assembled by a child. At least one first block element consisting of a rod made of a flexible material including a fitting terminal at one end or opposite ends thereof is provided. The fitting terminal has at least one fitting projection thereon. A second block element has a plurality of fitting holes each adapted to be fitted onto one of the fitting projections. The first block element and the second block element are combined with each other during an assembling operation so as to exhibit a desired three dimensional configuration. Each fitting terminal is provided with a plurality of fitting projections projecting from the outer surface of the fitting terminal so that the fitting projections can be selectively fitted into one of the fitting holes on the second block element. The rod constituting the first block element is composed of a plastically deformable core and a flexible sheath molded of a soft synthetic resin surrounding the core. The sheath is integrated with the core to form an integral structure. The core is composed of a wire-type material having shape memory characteristics.