Imagine a lego car with four wheels, you push it forward and the wheels roll and you move forward. I am wondering if there are any designs for a system or vehicle that when it moves forward it moves like an animal because of the forward motion being applied to it, not because something powers it and moves it legs so that it then moves forward. For example someone may have a robot cat that they made and when its turned on the motors, gears, whatever lift and move the legs and the cat moves forward. I am wondering if anyone has a design or knows of a product where if you did push the system forward, by nature of how that system is designed the system would walk the same way the cat was previously.
I understand this may seem like a stupid question but I have a weird/specific need for a project I am working on so any help is really appreciated.