Talking of the wizards - I love the discussion they have about Hogswatch in Hogfather.
That's a good one too. With the sockeater etc.
I think TP's greatest written line is (not funny but deep);
"Imo made us clever enough to work out he doesn't exist." - Nation
Have you seen what happens if you give this the "Da Vinci Code" treatment?
IMO (God) = Text speak. "In My Opinion God"
So we have a book all about atheism written by a self-confessed atheist.
The book is littered with atheist comments (will supply you with some if requested). It also hails Darwin as the "greatest ever scientist". It not only mentions Richard Dawkins (author of the excellent "God Delusion"), but calls him "nice".
However, the icing on the cake is the fact that the stars in the cave dated back 31,000 years.