This video has several interesting toy robots. Check at 7:00 when a bot draws by leaving a trail of sand. Center hole looks similar to the Scribblers which could probably do this too. Although probably necessary to drive in reverse, so the tail wheel doesn't drive through the sand.
"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."
- Pablo Picasso