The pursuit of knowledge does not always take us to pleasant places. It may lift us to dizzying heights, but may also drop us into dark valleys where no sane person should go.
Today we’re talking about fan fiction. Brace yourselves.
Let’s begin with the basics. Fan fiction is an amateur literary genre in which writers use worlds, concepts, or characters from other stories to tell their own.
At first glance, this doesn’t seem so bad—indeed, some fan fiction is actually quite tolerable. For example, many fan fictions (abbreviated fanfics) have been written and even published using characters now in the public domain, such as Alice from Alice in Wonderland and Sherlock Holmes. At its best, fan fiction is… all right, I guess?
However, most fanfics are terrible. Many writers of fan fiction lack the skill or experience to make good use of the ideas they steal from other stories. On top of that, too many writers use fanfics not to tell good stories, but as a cheap form of wish-fulfillment. Heck, there are entire categories of fan fiction devoted to fulfilling fans’ private desires.
For example, self-insert fics put the writers themselves (or fictional versions thereof) into the stories. (These representations of the authors are known as OCs, or Original Characters. OCs sometimes exist outside of fanfics, as many fans enjoy creating characters based on ideas or styles from existing stories.) Hurt/comfort fics inflict harm upon familiar characters, giving fans the emotional catharsis of seeing them comforted. Slash fics put characters in romantic or sexual relationships, thus upholding Rule 34 of the Internet: If it exists, there is porn of it.
(Here I must credit TV Tropes for its helpful information on fan fiction subgenres.)
Fan fiction can tell meaningful stories, but in practice, it hardly ever does.
Besides the problems with individual fanfics, fan fiction as a genre has two colossal faults. The first concerns law and ethics; the second, creativity and intellect.
Fan fiction is technically illegal. Companies hardly ever sue writers of fan fiction unless they try to publish their fanfics, and sometimes not even then. Regardless, fan fiction infringes copyright. It’s theft of intellectual property. For that reason, it has ethical as well as legal implications.
The second problem is more personal. Fan fiction represents relatively little initiative and creativity. Instead of creating new characters, situations, and settings—or at least pretending by renaming existing ones, changing them slightly, and using them differently—writers steal whole worlds from other writers.
Why do fans write fan fiction? I’ve already mentioned the aspect of wish-fulfillment. Some fans read or write fanfics as a way to delve deeper into stories they love, and fan fiction writers are usually guaranteed an audience within their fandoms. (Of course, conversely, they are usually guaranteed an audience nowhere else.) Like shipping and waifus, fan fiction is an enthusiastic outpouring of affection and interest toward a story.
In this post, I’ve been rather merciless toward fan fiction as a genre. I don’t mean to offend anyone who enjoys reading or writing fanfics. Heck, I’m as guilty as anyone. In years past, I read a few fan fictions, and even wrote a few. I still enjoy a lot of art, music, and webcomics by fans. We live in a culture of remakes and remixes, and fan works are part of that. Even unimpressive fan works are proof of how stories encourage and inspire creativity in their fans!

Fan works are at their best when they add something funny or clever to an existing work. In this picture, a fan of Calvin and Hobbes reimagined its characters as… well, Calvin and Hobbes.
Reading and writing fan fiction are valid hobbies. Creating it can develop writing skills, and reading it can evoke positive emotional responses. Fan fiction isn’t necessarily a bad thing… but I don’t believe it’s a particularly good one, either.