Now up to Pratchett's "Guards Guards". Once I get past "Eric", I'm at the point where the books are consistently good, instead of mostly hits and some misses.
Reading them all in a row like this, it seems like Pratchett falls into character tropes from time to time:
* The big, earnest, intelligent-but-dense young man who goes from Dwarf-like literalness to sublime understanding over the course of 300 pages (Mort, the kid from Small Gods, Carrot, Victor Tugelbund).
* The guy who's so good at being bad that he ends up being good for lack of being able to do bad things (Lobsang Ludd, Teppic 28, Moist, whatsisname from The Truth).
* A woman in a position where, though she is very attractive, you don't notice it because she's busy being important to the story elsewhere (Adora Belle, Sacharissa Cripslock, Lady Ramkin -- she's attractive to Vimes and Nobby, and apparently Lord Rust had an interest at some point).
* The Weasel (Nobby, Rincewind, to some extent Cohen the Barbarian although he's more likely to fight when cornered, the Dean of the university, Lupine Wonse, Moist).
* The character who is reformed, even though everyone else has stereotypical views of him/her (Otto Chriek, Detritus, again Cohen the Barbarian, Moist once more, the vampires in Reaper Man).
* The extremely powerful female character that everyone underestimates (Susan Death, Angua, Conina, Adora Belle to some extent, the woman who talked to the Duchess in "Monstrous Regiment", Mrs Cake).
There are others but those are the only ones I could pull off more than three examples for each.