Imagine a person wearing a cloak of invisibility flying a flying beast (e.g. winged horse, gryphon) which was also wearing a cloak of invisibility.
A race of people identical in all respects to humans except for the fact that they lay eggs.
A large forest which is the site of a research monastery dedicated to Silence. In the course of developing new spells, the monks frequently deaden all sound in huge areas of the forest, an extremely eerie experience for anyone passing through.
Small identical wooden or metal discs with a strange pattern engraved upon them (do not appear to be coinage). The discs can be found all over the continent; a farmer typically overturns several dozen when ploughing a field. Though they are unnaturally hard to break, they have no known use and are widely used as good-luck charms: almost all households would have them on the doors and on mantle pieces; many people carry one or more on them, bound on to a belt, necklace or sewn on to their clothes.
In the middle of an unimportant combat with some bandits a burst of wild magic transforms all of the PCs and their opponents in to random animals and monsters. They retain their intelligence (though not, of course, the ability of speech). They can either carry on the combat in their new forms, panic, or otherwise react how they see best. After about an hour, they return, unharmed, to their normal form.
The Californian Sea Otter, as a species, eats about 30 different types of food found throughout its range. Each individual otter, however, will only eat 3 or 4 of these foods - those it was fed by its mother as a child. It will not eat the others even if failure to do so means it would starve. Maybe other, possibly larger and more dangerous creatures and monsters, have similar habits.
Walking through the alleys of the docks district of town, you hear an old, mad beggar calling out for alms. He claims to be a god, cast out from heaven and stripped of his powers. The party passes, tossing a few coppers to him. In thanking them, the madman refers to incidents in their childhood or distant past which would have been all but impossible for him to know.
A continent is home to large, leathery flying beasts with a wingspan of over 70ft. Though shy, herbivorous and easily scared, it is possible that an enterprising person could domesticate them. They would be useless in war due to their timidity, but excellent if used for commercial air travel.
A dark necromancer has discovered a way of making the magical energy cost of resurrection less than the energy he can gain by draining their life force. Given a sufficient supply of mind-drained minions, ultimate power beckons.
An old, misanthropic and paranoid man feels his time is coming. There are sons to leave his fortune to, but they are not worth it, not a dime do they deserve! And he doesn't really trust anyone else. And so he has made a decision: as a part of his last will, his henchmen are instructed to burn and destroy all his holdings, buildings as harvest. The lands shall be auctioned off, the proceeds used to pay the servants. Nothing shall stay behind. Nothing.
Depending on the status of the grumpy old man, this weird occurrence may be only a family drama, or it may end up bringing an entire region into chaos. Or the son(s) have found what should happen, and want to prevent it before their sick father dies.