I would write a fanfic on Luna Lovegood and Neville getting in a relationship after the battle at Hogwarts and rehabilitating Frank and Alice Longbottom using Luna's crazy ideas and they getting better due to her care.
We all love some fictional character or the other. If given a chance to write a fanfic, or change some things about a fictional character, what would it be? Come on, write your fanfic here!