Maybe it's a dragon, maybe it's a powerful sorceress, maybe it's a proficient gang of mercenaries.
They arrive at an old castle, or a comfy cave, or a decayed manor, and decide to install themselves for a while.
They demand tribute from the local population. You know, a constant supply of food and firewood, clean clothes, maybe a few servants to tidy and fix up the place and run errands while they're there.
Not much later, people start to show up and make reasonable demands. The locals can hardly give them food if some monsters are ravaging the farmlands, now can they? Or help rebuild the dam, or help solve disputes as impartial third parties, or defend the locals from bandit raids, etc.
Maybe they know of better ways to do things, like better farming or architectural techniques. Maybe they have some medic knowledge and help when a local gets hurt.
People are content about this relationship, and they're slowly accepted as the new rulers. Maybe people even ends up liking them better than whoever was before, good management it's so hard to find, after all. Bonus points for comedy if they're completely oblivious of these people acceptance.
^An example of the kind of stuff I'm looking for
by LordXamon