I'm actually amazed that my over used plot hook was not mentioned . . . I thought it was the old standby for EVERYONE:
The [village, town, city, country, continent, planet, multiverse] is threatened by [humanoid, dragon, demon, devil, aberration, wizard, cleric, sorcerer of choice] and the [village elders, town council, city rulers, king, emperor, world-ruling cabal, gods] ask the less powerful PCs to resolve the issue because [s/he/it/they have this other thing to do and can't be bothered with it right now].