Still testing the hypothesis...
Off the shelf...
"The Penguin Book of Curious And Interesting Mathematics" By David Wells.
Looking looking, ok...there's a story in here about Charles Babbage and a pal almost accidentally ordering 50 eggs at a rural french restaurant due to an accent mixup. Then, before he'd gotten to Paris the story had already gone through telephone-game flanderization until the story was that he and his pal had ordered and eaten 52 eggs and a pie.
So here's a spell:
Level: Cleric 1, Wizard 7
Saving Throw: No
The caster casts this spell and then relates a true story to someone. This someone (who must be able to understand the story blah blah etc etc) will be compelled to re-tell it to at least one person and exaggerate it. Everyone who hears the story will, in turn, re-tell it and exaggerate it in turn until the caster chooses to end the spell. When the spell ends, reality will be altered such that the exaggerated form of the story is now true, with all the effects on reality that would imply.
The caster must allow the story to grow for at least one week, but may allow it to expand for months, years, decades, or even centuries--if s/he is able to find a way to stay alive that long. The longer the story is left to grow, the more exaggerated and thus powerful it becomes. (GM's discretion on exactly what form this exaggeration takes.) The caster may check the "progress" of the spell at any time by asking appropriately gullible locals if they've heard the story and what exactly they've heard.
The only way to prevent the spell from taking effect is to kill everyone who knows the story before the caster ends the spell. Under ordinary conditions, the story will spread at a rate of one new believer per day.
This spell cannot be recast by the same wizard or cleric while a previous enchanted story is still circulating.
In other random-inspiration news, I walked the dogs today.*
Ok: Gerard De Nerval used to walk a lobster. This, in turn, was, I believe, derived from the practice of aristocratic women of earlier centuries walking lobsters as a show of conspicuous time consumption.
The nobles of Vornheim walk small flail-snails, naturally.
Implying they have breeds, varieties, subspecies of flail snail. And painted shells. And beadazzled shells.
Common expression in Vornheim: I wish I could walk that lobster. Meaning, like, to expend effort on a frivolous task.
Also, Mandy watched Warlord with Jet Li. It is chock-full of D&Dable ideas. I hesitate to enumerate them here lest it prevent you from being forced to watch it yourself.
*(Bug and Drax The Destroyer).