Where's My Cow?

Not exactly the book mentioned in Thud, this book uses three distinct art styles. It tells the story of the time (mentioned in Thud) when Vimes changed the story to a more "city appropriate" version, removing the animals and putting in city people. The first, most realistic, art style is the real world events. The second, highly simplistic, is for the Where's My Cow? book itself. The third is a cartoony style that anthropomorphesises the toys and paintings, a visual description of young Sam's imagination. As young Sam gets more and more worked up the art styles blend together.

This work shows examples of

 * Defictionalization: The book in this book was just a Book In A Book until it was made for real.
 * And try say everything before "until" ten times!
 * Seeing as both books were released concurrently in Britain, more of a tie-in.
 * There was barely any delay in America, as well, and they were marketed as a tie-in during Pterry's signing tour.
 * Please Keep Your Hat On: In possibly the first ever illustration of him sans Watch helmet, Samuel Vimes is revealed to have greasy helmet hair.