Here is another stupid simple idea I came up with a few years ago and works better than I imagined. I had this toy from childhood. I believe it was called a giggle n rock ball. I found a second one at a garage sale. Simply turn it on (it takes batteries). Place it in a cardboard box a little bigger than the toy and seal the box up. Let the box bounce around on the driveway or other hard surface. You could right "DANGER" or "DO NOT OPEN" all over the box. The ones that giggle are even better because it sounds like muffled cries from inside the box. It bounces for about 30 seconds and then stops and giggles and repeats.