One of the things that is very popular in the fan fiction community (of any fandom at all) is the creation of alternate universes (also known as AU’s). AU’s can range from just one little aspect in the story changing and seeing how that affects everything else, to giving the story a completely different setting or setup or even changing the characters’ personalities for whatever reason (like making good characters bad or vice versa).
Some people might think that there’s no point to doing AU’s, that they’re just dumb and taking away from the intent of the original story, or are just flat out ridiculous. In some cases that is exactly true, but you shouldn’t be knocking them as a whole. As I said, people in fan fiction communities like using AU’s, but recently I’ve discovered it can be a good tool for writing your own original fiction as well (especially for really long series you might be working on).
AU’s are a chance to explore your story or characters or even themes with a completely different perspective. Maybe you could take that medieval fantasy story and make a modern AU out of it, so essentially the same basic plot happens, but it’s set in a modern time period, just to see what changes in both the characters and the plot itself. Maybe in your story, your character(s) made a huge life-changing decision. What would have happened if they had decided something else instead? How much would that have affected the story?
These are the sorts of things you can explore by writing AU’s for your own stories. It’s fun and intriguing and it honestly will give you a better understanding of your characters and plot by working with them in these different settings, so long as you maintain an understanding of how they’re supposed to be in-canon vs. the AU and not changing things to make them do completely out of character stuff and let your mind be clouded by that. (not that I’m speaking from experience or anything, nope, not at all)
Now, of course, you’ve got your intriguing “what if” AU’s, but then you’ve got other sorts of AU’s. There are crack AU’s, and there are what I would call fan fiction AU’s. Crack AU’s are basically just coming up with random and silly things, and there is literally no point to them except to make you laugh. There’s nothing wrong with that. If you’re having fun with it, by all means, continue! Laughter is good, especially if your stories are usually filled with pain (again, not that I’m speaking from experience *cough*). Fan fiction AU’s are when you do one of two things: crossover your own original story characters with a fandom of your choice (literally fan fiction), or do something along the lines of a fairytale AU, which would be putting your characters in the story of a famous fairytale and seeing how that works.
In the case of the fairytale AU, and things similar, I find those sorts of things a good way to explore themes of your story in a new light. Perhaps you’ve noticed something about your story or characters that just reminds you so much of that fairytale, so you take them and insert them directly into that fairytale and see how they work within it. You can do this kind of thing with other stories that aren’t fairytales as well. Just inserting your own characters in place of the original characters of the story (again, why I’m calling these fan fiction AU’s).
Basically, AU’s have a lot of potential for further developing your characters, your plots, and your themes. They should be used wisely and not abused, and never mixed up with the original canon version of your story. But they’re fun and they can be quite enlightening. Take it from me, because I have a million AU’s for one of my own series.