I started reading Colour of Magic when I was about twelve, and it delayed my eventual discovery of just how amazing Discworld was by four years. Nearly ten years later and I've still not finished it. It was Tiffany Aching and the Nac Mac Feegle who got me over the aversion, in the end.

Somewhere there is a fic that followed the basic premise of Jack Harkness, the Librarian and Death walk into a bar in Cardiff. It was more cracky-crossover than all-out AU, anyway, and now I can't find it for the life of me. Figures.