Hmmm . . .
One of these sorts of lists is always going to cause dispute. For example: Vetinari, CMOT, The Librarian, The Luggage - these are all what I would consider background characters. Yes, they appear frequently, but they are hardly major characters. I put Granny Weatherwax higher than Death and Sam Vimes and Tiffany much higher than they have them. If you are going to include minor characters, then I'd put Ponder Stibbons on there as well.
“Men never commit evil so fully and joyfully as when they do it for religious convictions.” – Blaise Pascal