One of the most popular demo lessons I do in schools is about writing Fan Fiction. I first learned about Fan Fiction twenty years ago at the state Gifted Ed conference from a woman who wrote Dr. Quinn, Medicine Woman fics. For the past few years I’ve been offering Fan Fiction as a choice, but fewer than a quarter of the students I work with request it.
And then I started reading released items from our state test. Colorado’s test is aligned to the PARCC assessments and the CCSS. Turns out, knowing how to write Fan Fiction is a truly useful skill set given the narrative tasks students are asked to complete.
So while it is awesome to play with Fan Fiction as a way to prep for state testing, it’s actually a fantastic way to introduce fiction. Why? Because telling students (or yourself for that matter), “Write whatever you want,” is too much, too big, too ambiguous. Fan Fiction sets up lane lines or those bumper thingies struggling bowlers like myself need, to give you a straight shot down the middle of a single scene.
Here’s an example I often use with older students and adults. Think about when we first meet Draco Malfoy on the page or screen in the first installment of Harry Potter. We know Draco is a bully and probably a villain. But later when we meet Draco’s father, Lucius Malfoy, the reader/viewer gains insight into why Draco is the way he is. The fanfiction assignment is to write a single scene showing a typical family dinner at the Malfoy household. Make a decision where in the timeline to set this dinner (what year is Draco at Hogwarts, is Dobby a free elf, etc.) and off you go.

A cosplayer in the vein of the Fantastic Beasts and Where to Find Them film
Several classrooms have taken this simple idea and written for days. For a beginning fiction writer, Fan Fiction offers pre-made characters with pre-established relationships in a known setting. All the writer has to do is invent dialogue and practice describing things.
An Archive of Our Own is the most popular fanfic site right now. It’s full of interesting fics from over 36,000 fandoms. Pay close attention to the tags – these will/should help you find what you’re looking for.
This is a link to a Fan Fiction plot generator.
Here’s a Pinterest page full of Fan Fiction prompts.