Long time no see! Well, my sister came across this fic on ff.net and after showing it to me and whipping out our copy of The Truth for verification found that "Wherefore Ducks? And Other Stories" by Gogol has lines of the novel lifted almost word for word without giving credit where credit is due. Lots of dialogue, and even the first two paragraphs of the fic are entirely Pratchett.

The link, for those interested: http://www.fanfiction.net/s/4106592/1/WhereforeDucksAndOtherStories