Are you a writer? Do you have a shallow, obnoxious, petty character who needs to grow up already?
Turn them into a llama.
That’s right, The Emperor’s New Groove style.
(If you’ve never seen that movie, it’s excellent.)
How do they react? Are they horrified? Annoyed? Traumatized? Mainly concerned with what this has done to their appearance?
Set it up so your nicer characters have to help the obnoxious character figure out how to turn back into a human. Are they actually nicer? Do they help willingly? Or are they glad to see the obnoxious character suffer?
Put as much or as little thought as you want into the logistics of it all (after all, this is unlikely to end up in the official story), but make the solution complicated enough that everyone has time to grow in the process.
I did this recently with a character, at my friend GG’s suggestion. We decided everyone needs to try it. It was, first of all, a lot of fun. And it was fascinating. I wrote it from Obnoxious Character’s point of view, a perspective I never use in the actual story. This was both difficult and eye-opening, because there were things I knew my usual point-of-view characters were doing that I wanted to write about, but Obnoxious Character did not notice or care, so I couldn’t. But she was forced to slow down, get to know the main characters better, think, and notice some of her own problematic attitudes.
In her real story, Obnoxious Character will not turn into a llama. But playing with it gave me an idea of what a less obnoxious version of Obnoxious Character looks like and how my other characters interact with her while she’s changing. It helped a lot.
Fun, fascinating, and helpful. What more can you ask for in a writing exercise?