A toy for a pet generally includes a housing defining an opening, and an insert configured to fit at least partly within the opening of the housing. The insert is expandable from a first configuration in which the insert is capable of freely moving into and/or out of the opening of the housing to a second configuration in which the insert is inhibited from moving out of the opening of the housing. In some aspects, the insert is configured to substantially fill the opening of the housing when in the second configuration. In some aspect, the housing may have multiple openings, each capable of receiving an insert. And, in some aspects, the insert is expandable from the first configuration to the second configuration by heating the insert or exposing the insert to microwave energy.
