When you play with a doll or a Hot Wheels car, there's nothing to tell you when you're finished. It's quite unlike a board game. Still, the form of the thing constrains what you do with it in some way -- a doll doesn't roll on the sidewalk the same way a car does, and cars generally don't have faces. A good part of the fun comes from exploring all the different things you can do while you're constrained in that particular way.
I'm interested in creating roleplaying toys.