Readers of a certain age will recall the contribution made by Fred Flintstone, the caveman in the '60s cartoon series, to a cleaner environment. The Flintstone family rode down the street in a car powered not by fossil fuels - fossils were then in their infancy - but by Fred's feet.
Or think back to The Little Rascals and their transportation innovation; a car powered by a dog chasing a rabbit on a treadmill.
Those cars were comical because they were impractical, but they were green by comparison to Detroit's tail-finned products.