What is the theme in The Light Fantastic by Terry Pratchett?

Pratchett uses a variety of fantasy clichés in order to parody the fantasy genre. He uses so many clichés and in such a humorous manner that he gives them new meaning. However, in the Discworld, these are not clichés, but part of reality. Sometimes Pratchett takes this further when TwoFlower mentions something that the reader recognizes from fairy tales and one of the Discworld characters shrugs it off as pure fantasy. For example, Twoflower thinks Druids are good people, when actually in the Discworld they are bloodthirsty.