Shrinky Dinks reached their height of popularity in the 80s. They were an activity set for children consisting of large flexible sheets, which once baked in the oven, turn into smaller, hard plates or pieces of jewellery. Many of the sets were themed on popular children's characters, which you could have fun painting them in before baking.
The toy set itself was invented in 1973 by Betty Morris and Kathryn Bloomberg, who were devising a boy scouts toy for their children. They went on to be sold in local shopping mall, then by larger toy manufacturers under the title Shrinky Dinks.