Plastic pants, plastic panties, an diaper covers are all basically the same thing. They are devices worn over a diaper for the purpose of containing liquid or solid waste that may otherwise leak through the fabric. They are most commonly worn with cloth diapers, although sometimes with disposable diapers. Today, "plastic pants" are usually made out of vinyl, plastic or, in some instances, the traditional rubber. The original diaper covers were made from wool, which was naturally waterproof.