Penny Racers have been available for a long time and are still available in stores to this day. They were small (about one inch) cars made of plastic and had a pull-back motor inside. The trick was to insert an American penny in to the slot near the rear bumper of the car before pulling it back and letting it go. The penny would act as a weight and allow the Penny Racer to do all sorts of wheelies and other tricks. Different sized coins would produce different tricks.