1. Interlopers from an alternative dimension are attempting to murder and replace key inhabitants of the city. So as to better identify their fellow conspirators, they have taken to wearing a distinctive style of beard. 10% chance the new fashion catches on with the broader populace.
2. An person from an alternate timeline switches places with his NPC counterpart. He knows the true identity of the Purple Plane Hierophant and the hidden location of the Vault of Zumarios. His relationship with any PC's may or may not be similar.
3. A well known and loved hero has suddenly taken to acts of rapine and cruelty. Attempts to cast Remove Curse and similar magics have all failed to restore him to his former self. He has been seen entering the compound of an obscure cult, whose members play harps and espouse a coldly rational philosophy.
4. When utilizing a means of teleportation during inclement weather, there is a 1% chance that the Vancian Intelligence affecting space/time will come into contact with a version of itself in an alternate reality. There will then be a 10% chance of a psychological entanglement, causing any beings which are teleported under such conditions to swap places with their counterparts.
5. An attempt to summon a legendary hero goes awry. Any PC or NPC of 9th level or above must Save vs. Magic or be replaced with a doppelganger from another dimension.
6. As the self styled Dread Empress is in the midst of her conquests, she suddenly begins altering her usual way of carrying out her plans. Showing mercy, instead of cruelty. Choosing diplomacy over war. Her lieutenants are disturbed.
7. Upon emerging from the dungeon, the party finds the world has turned upside down. Former allies are now enemies, once great empires have been brought to ruin and once wise rulers display madness and cruelty. Banners, heraldry and social customs have all changed.
8. The Dagger of the Octagonal Mage has been carelessly left laying about in a dungeon. Anyone bearing the blade will shift places with a counterpart from another dimension, every 1d8 days. Class, alignment and any other attributes may change at such times, at the DM's fancy. There will be a total of Eight such counterparts involved, inclusive of the PC or NPC finding the dagger.
9. The Oculus of Barimor will expose anyone spied upon, if they are not native to the dimension of the owner.
10. A fantastically powerful ship from the Terran Empire enters orbit around the planet and demands complete obedience from all inhabitants. The captain, who appears half elven, demands access to several abandoned mines, where worthless crystals are all that remains of what was once a treasure trove of minerals.