The past few years, someone I follow on Twitter named ZandraVandra has been having a Light Novelber jam in November, like a lighter version of NaNoWriMo. I entered, intending to actually write something in November. There was a link to a list of writing prompts, and one that stood out to me was about spending Halloween as a ghost. My initial thought was to try to somehow make the ghost a metaphor for derealization and write a fairly serious story, but I couldn't figure out any other details of how the story could go besides that, and when I get stuck like that I tend to procrastinate. Also there were other things taking up some of my time in November.
By the end of November, no one had entered (I'm guessing maybe 2020 was particularly hard on the people who would have entered maybe?? I don't know, just speculating), but they extended the deadline. During that time, Zandra started streaming Super Mario World, and talked about the blocks that transformed into ghosts, and that inspired me to make that a part of my story, and it ended up being less serious than my original idea.
Note that the story isn't true to the game. Magikoopas turn blocks into enemies, and there are blocks that transform into ghosts, but Magikoopas in SMW don't turn blocks into ghosts, just yellow koopas and thwimps (and coins and 1-ups). I'm not sure if they can create boos in later games, though, and there might be some fangame or romhack out there where they can create boos, but if so, I'm not aware of it.