So unless you’re writing self-inserts or original characters, fanfic is partly about getting into the headspace of a character you didn’t create. That, for me anyway, is one of fanfiction’s chief pleasures — I’ve written before that for most fans, fic isn’t about wacky plots, as people outside fandom often assume, but about understanding a character so well that the interesting part comes when you stick them in a wacky plot (sure, “there’s only one hotel room left” counts as wacky), apply pressure, and see how they react.