When I was growing up, I had a toy slinky. It was a coiled piece of plastic (or sometimes metal) that shapeshifted it's way down the stairs. Flipping and flexing. The slinky also got adapted to be used as a skipping rope at times ( Don't think it was made for that?). Became a bungy jump for various action toys off bridges and I even found the odd slinky lurching towards my face, unleashed from a friends hand, to get whipped back and recoiled at the last moment before impact