How about a dragon how cheerfully rules over a kingdom; his people all know him for what he is, and dragons are looked upon as wise and benevolent creatures. Dragonslayers from other kingdoms coming to free it from 'tyranny' are likely to get beaten to death by peasants with cast iron skillets.
Someone needs the blood of a dragon, given willingly, to make a rare potion. Guess who gets hired to sweet-talk a dragon into giving up some highly powerful blood?
The members of the party has unknowingly been infected by a mysterious plague and have been spreading the virus for quite some time now while adventuring. They start to hear rumors of all the cities in quarantine after they travelled trough. Will they discover the source of this? Will people start to avoid them, try to kill them?