Shape-memory metals get a fair amount of attention, but shape memory polymers exist, too. In fact, heat-shrink tubing is a familiar example of a simple shape-memory effect in a polymer. This video uploaded by MIT researcher Vikas Srivastava back in 2009 is a more impressive demonstration of heat-induced shape recovery. The plastic material is tBA / PEGDMA, which has a shape-change temperature that is close to human body temperature. It’s under investigation for use in medical implants. The referenced paper is freely available as a PDF.