Shrinky Dinky's Shrinky Dinks were a craft toy in the late 70s that happened to be given away as a cereal gift. I got a box set for christmas. It had sheets of a thick plastic which you could use your own or provided pis to draw and colour in then shape to make key rings ,pendants etc. Putting them in the oven melted them to become solid plastic and the colours more vivid. Loved them!