The last D&D campaign I ran, I wanted some idea to have so different people (the PCs) join to adventure together, and that it wouldn't involve meeting in a tavern. As such, I slightly modified their backgrounds, and designed an adventure to that end. So:
1) I decided that all the PCs came from the same mountainous region, held by a clan-like community (i.e.: a Scottish clan, something like "Mac Leod"). But as the characters were much different, I said they were from remote parts of the valley, and thus were unknown to most people in the community. Then, the gnome illusionist PC would be a wandering peddlar and his wagon who happened to be there at that moment.
2) The plot was that the clan leader was too old (according to clan's laws) to continue being the chieftain of the clan, and would have to resign and designate a successor during a clan's meeting. However, he didn't want to quit, and thus had told that his son would soon come back home and would be designated as the new leader.
Unknown to all however, was that the son had left for good, not wanting to have anything to do anymore with his tyrannical father. The clan leader knew that fairly well but didn't care, for he had instead ordered a set of Elixirs of Youth from an alchemist. He truly intended to become youth again, pretend to be his own son, and be his own successor.
Unfortunately the alchemist had been attacked by brigands who had stolen the magical elixirs. So, the clan leader had to ask some people to help him recover them. And so he did choose the PCs for they were unknown to most people in the community, were from remote parts of the valley, weren't too much experienced (2nd level), and so could probably be easily get rid off after they would bring back the potions.
All of this may appear as a weak plot, but the point was to have an excuse for putting the PCs (who didn't know each other) into adventuring together. On the other hand, the reason for the clan leader believing this ridiculous scheming would work, was that being too old he was also becoming senile...
3) Long story made short: the potions would not be found. The brigand leader had consumed them, and as a result become a young boy again. Now as he had been a bully with his men, those took revenge on him as he had become a helpless child. It's when the PCs intervened, killed the brigands, and saved the helpless child, protecting him during all the adventure thereafter. This was real fun when the PCs eventually realized who this strangely vulgar boy was, and that the potions were lost forever. Plus the old clan leader died from heart attack in learning it.
