Writing fanfiction is great because you get to channel all your brainpower into your absolute favorite characters. You get to take them and put them in a situation and think seriously and intensely about how they would react to it. You get to examine them and their thought processes and their insecurities and their values and you get to measure and weigh them and then you get to manipulate that situation literally however you want! You can test them! You can make them ridiculously happy! You can hurt them in ways that they’ve never been hurt before and then (if you’re like me and can’t stand unhappy endings) follow them through their recovery from that pain! You can write them into experiences that mirror your own or you can write them into situations that are literally impossible and you can write them into situations that would never happen in the source material. You can write endless AUs, pair your faves with literally any other character and explore their relationship dynamics (!!!!!!!!) and you can follow them through endless journeys because your interaction with them doesn’t end when the source material ends. You get to carry them with you. And your appreciation for that character and your understanding of that character can grow SO MUCH just by being in their head for a little while.
tl;dr: FANFICTION is so COOL