Word of God: Jim Butcher is quite often going to conventions or signings or readings, and occasionally pops into threads on his own forums, and willing to answer questions. Most of the time he gives a straight answer, it's because it's information that will not make it into the series. His forums have special sections cataloging various "Word of Jim" posts, speaking on everything from how different wizards may perceive things in the Sight (Ancient Mai might perceive a warlock as a dried out, bleached white tree, while Listens-to-Wind may perceive the same warlock as smelling foul), to characters' pasts (Ebenezer McCoy and the Merlin fought on opposite sides of the French-Indian war), to background information that would explode if Harry knew about it (Ivy's true purpose in the Oblivion War).
In regard to the TV show in particular, Butcher said Bob was originally killed by an axe to the head and mentions the skull prop has a hole in the back for that reason. You can see the hole in one shot during the series.