NB – This post contains LOTS of spoilers. Be warned.
I think one of the reasons I love Pratchett so much is that I dearly love a good story, and Pratchett is a storyteller par excellence. The Discworld and all the magnificent characters within it all spring from the drive to tell a brilliant story, and, as with all the best stories, are like a Chinese puzzle, containing stories within stories within stories, some barely glimpsed. Almost all of Pratchett’s characters, however minor, come complete with a entire, and entirely appropriate, back-story, some of which would quite happily drive whole novel series in their own right.
Take Captain Carrot, of the Ankh-Morpork City Watch, for instance. Carrot is a text-book hero, called Carrot not because he is ginger but because he is shaped like a carrot, very wide at the top and narrow at the bottom. He is kind, intelligent, brave, skilful, handsome, polite, charismatic, gentle and unselfish. He is also a dwarf, despite being about six feet ten inches tall, because his parents were dwarves. He is, of course, adopted, having been saved as a baby by the dwarves from bandits who had attacked and murdered a party of travellers, all save Carrot. It becomes fairly clear throughout the course of the books that Carrot is the lost heir to the throne of Ankh-Morpork, although this is never explicitly stated and it never becomes central to the plot of any of the books. It’s just there, Carrot’s back-story.
As an example, this is a pretty good example of two of Pratchett’s favourite devices. One is the character who confounds your expectations; the tall dwarf, the law-abiding werewolf, the vampire who becomes a photographer because he is in love with light. And these are not just jokes, but things which are central to the characters; Pratchett creates the characters and then builds them around their contradictions, joyously exploring the tensions and problems that result.