Try as he might, illustrator Jake Parker couldn’t make sense of the world that Pixar created for Cars. He writes:
And that leads me to the one thing that didn’t sit well with me: the strange machine/flesh hybrids Pixar came up with to populate this world. It’s as if a mad scientist enamored with automobiles terraformed Mars and furnished it with cyborg vehicles with engines of steel and minds of flesh. You have these cars, but with actual fleshy eyes, with irises, and mouths of teeth and tongues. Where does the machine end and the flesh begin? So, to make everything piece together a little better in my head I drew up what I think the internal structures of Lightning McQueen might look like.
This amusing illo is what he came up with (link to larger image).