Since I will probably guest mod, I'll post stories here to avoid confusion. I'll move the first story over here in a minute
Okay, first one:
What if instead of folks being told to stay inside, every single person over a certain age was assigned their own giant plastic hamster ball to get around in outside the home? (Or some other artificial device to keep people a minimum distance apart?) Imagine someone growing up this way who accidentally breaks their hamster ball.
A villain is on the verge of implementing their plan (world domination? dumping blood on someone at prom?) when a world/country/state/city/company/school-wide event turns everything upside down and has everyone involved acting in ways that the villain hadn't planned on. How do they react to the change?
Here's another exercise for you!
A large number of museums have put virtual tours up online, if they didn't already have one. (Here is an article with links to a few, but feel free to search for others.) Go 'wander' around a museum and find a piece you haven't seen before that catches your eye, and imagine a character who has come to life from that piece suddenly finding themselves outside that museum. Write their story!