Like everything we would do when we were kids, before phones and gameboys, there was a the heavy application of imagination. Something to make the drawn out time fly, especially on 4 hour car trips that felt so much longer than they do today.
I was told that many people when they were kids imagined a person or thing running alongside the car on longer stretched of highway. This one was mine. Ran on all fours on divides, over cars and power lines. He had armor just in case he tripped or fell, a part of him that might work like a bunker's shutters closing. Everyone makes a whoopsie once in a while, right? He'd be able to run circles around the car. Full speed the other way and back in seconds.

Just remembered what might be an imaginary friend a lot of people had. Tried to put in a kid's coloring book kind of background to pin the look. This is what I had in mind when I made Duncan. Why do you think he's a cheetah?