Just watching the Half Blood Prince this morning, and Professor Slughorn is hilarious! Of course my mind pops right to D&D, and thinks boy he'd be a funny NPC to play. Every play a specific character in your game? maybe with a slightly different name. I can imagine him being a wizard that lives along in a tower. Maybe the PC's have to meet him to find a specific ingredient, possibly. In the Harry Potter world he's an alchemist, so I would have to keep that in mind. Maybe I'll build a Character class around that? More thought is required. Personally I'd prefer to play a more interesting bumbling character like Slughorn, rather than a gandalf copy, but that's just me.