The characters within a book were, from a certain point of view, identical on some fundamental level ‒ there weren't any images of them, no physical tangibility whatsoever. They were pictures in the reader's head, constructs of imagination and ideas, given shape by the writer's work and skill and the reader's imagination. Parents, of a sort.
Jim ButcherDo you have a little white dress? I've had this deep-seated nurse fantasy about you, Murphy.
Jim ButcherHe gave me an inscrutable look that said maybe he would and maybe he wouldn't. Mister was a cat, and cats generally considered it the obligation of the universe to provide shelter, sustenance, and amusement as required. I think Mister considered it beneath his dignity to plan for the future.
Jim Butcher