What is a head canon? Well, it’s one of those terms that I’m sure people would argue over, but it tends to come up in fanfiction to refer to things we don’t actually know to be true in the canon of a story, like Harry Potter for example, but because of what we do know, in our minds we believe this (whatever it may be) to also be true.
Still using Harry Potter, as most people are familiar with it, since I always wished there was more Marauders in the books, a head canon could be a whole plot line idea for a story about them going out in their animal forms causing a ruckus or doing some prank, that we can easily believe might have happened or could happen in actuality because everything about it is still in line with real canon.
Head canons can also work if you want to imagine an alternate universe for something. Given what we know of the universe of Harry Potter, if Neville had been The Boy Who Lived instead, how would the story have been different?
Coming up with or writing out head canons doesn’t require you to write a full story, just jotting down notes, in a way, with maybe some paragraphs here or there, or even snippets of dialogue, but you’re really just trying to get the idea out of you as quickly and succinctly as possible. Maybe you’ll come back to it someday to write the story out fully, maybe getting the idea out of you is all you needed to feel that moment of catharsis and that’s as far as it will go. Maybe working out a head canon is what inspires you to consider your next original story. Whatever the answer may be with any given head canon exercise…it’s a lot of fun.
For me, I find that once I start allowing for head canons to come to me, and take the time to write them out, it happens more frequently, which then in turn gets the muse going to come up with ideas for my original works.
Try it out! Suddenly realized that two of your favorite TV shows have a lot in common and one could totally be an alternate universe of the other? Describe to yourself how that would work and what the story would be. Want to consider a what if, such as the hero being the villain and the villain the hero? How would that go? Write it! Give creating a head canon like this a try once and I guarantee it will be your new favorite way to waste time, BUT! Might also help inspire you with your regular writing.