Of course, fanfiction writers don't limit themselves to the characters of their own universe. You have "crossover" fan fiction where, say, the CSI: Miami crew could end up enlisting the help of Buffy the Vampire Slayer to identify a forensics clue, or Harry Potter could meet Jacob Black in the forest and fall in love under the moonlight.
You know who else likes to write that kind of ridiculous mashup? Hollywood screenwriters.
"OK, so how about Voldemort and Hitler decide to open up a bed and breakfast in Fraggle Rock?"
Hell, television has been doing crossovers so often that they're cliche. A detective from Law & Order appeared on Arrested Development, CSI visited Without a Trace, characters from The X-Files turned up on Cops, and Lurch from The Addams Family popped up on the old Batman show. Syfy Channel shows Warehouse 13 and Eureka went further, making two characters from the separate shows fall in love. It's also around in movies: Alien vs. Predator, Freddy vs. Jason, and even Disney and Warner combining in Who Framed Roger Rabbit. The comic world has given us equally strange crossovers: Spock fighting Wolverine, Lara Croft facing off against the Wolfman and Dr. Doom teaming up with the Decepticons. And of course, there's Batman and Superman's erotic crossover:
Marvel and DC also did something far weirder than even Internet fans ever came up with: combining separate fictional characters into one. So Wolverine and Batman were put into a blender to create Logan Wayne, the Dark Claw:
Once again, the only thing here holding back an even bigger, more perverted wave of crossovers is not restraint or taste, but legality. The creators of Freddy vs. Jason wanted to end the film with both characters going to hell and meeting Pinhead from Hellraiser. They couldn't because they didn't own Pinhead's character rights, not because a producer looked at it and said, "No way; that sounds like something you would find at the edge of the Internet."
The "Mary Sue" is perhaps the most infamous character type in fanfiction. A Mary Sue is a thinly veiled representation of the author, or more accurately, the person the author wishes she could be. Her main characteristic is her utter amazingness, which is so strong it creates a kind of black hole that sucks in the established personalities of the characters around her.
"I don't know what I love most about you, Raven: The fact that your eyes constantly shift in hue, or the fact that you're secretly a half-dragon survivor of domestic abuse."
Wise characters are baffled by the Mary Sue's superior intellect, emotionally distant men cave in and fall in love with her, cold characters are impressed by her tragic past. She usually features a striking appearance and unusual name and spends her days surrounded by people telling her how wonderful she is.
Mary Sues can be men, too. One appearing in the original Star Wars trilogy, for example, could easily outshine Yoda in the Jedi arts and would have blown up the Death Star himself, except that he already used his wiles to talk Anakin out of being evil. One step down from a Mary Sue is self-insertion, where a fanfiction writer doesn't even bother to disguise his character behind a better-looking mask. Instead, he simply writes himself into the story, like this 15-year-old boy who is mysteriously transported to Pandora and feels himself falling for a seductive Na'vi woman as soon as he gets there.
"My people are all about acne."
It's the literary equivalent of playing pretend, but for adults, and usually based around sex. In other words, it's long-form masturbation.
But don't laugh; by every account, a writer of Mary Sues is now one of the richest authors on Earth. The Twilight novels by Stephenie Meyer fail the Mary Sue Litmus Test miserably: Main character Bella Swan is so charming and attractive that a vampire who has remained a virgin for a century instantly falls in love with her, and several other boys fight him for the privilege. If that's not clear enough, another Stephenie Meyer novel features a protagonist named "Melanie Stryder." Too on the nose?
It must be hard for her to do all that writing one-handed.
Another popular book series, the Millennium trilogy by Stieg Larsson, centers on a Swedish journalist whose life mission is exposing corruption. Coincidentally, this was also exactly what Stieg Larsson did. His fictional version, however, is also fabulously rich and talented, admired by many important people and constantly being seduced by beautiful women, including a former abuse victim whose fear of men is cured by his boner.
There's also the young Star Trek: The Next Generation character who routinely uses his extraordinary talents to save the lives of older, experienced crew members and who is even named after series creator Eugene Wesley Roddenberry:
This self-insertion has been going on for centuries. Dante's Inferno has Dante meeting his dead hero, Virgil, and then running into a bunch of his enemies, who not only admit that they were in the wrong but are actually now suffering eternally in hell. Agatha Christie had a female crime novelist show up to help Poirot with his cases. Stephen King, Robert Heinlein and Geoffrey Chaucer all turn up in their own writing to have adventures and prove to a bunch of fictional people how awesome they are.
Ultimately, the Mary Sue scenario is just fanfiction taken to its logical conclusion, because we are all die-hard fans of some fictional universe we'd love to see and experience, but we are even bigger fans of ourselves. The Mary Sue allows everyone the opportunity to shed the character flaws and limitations we suffer through daily while simultaneously transporting our better selves to a utopia where, if we're very lucky, we have hard, fast sex with Sonic the Hedgehog.
Read more from C. Coville here.
For more on fanfiction, check out The 5 Most Baffling Sex Scenes in the History of Fanfiction. Or learn about some fiction that came true in 6 Eerily Specific Inventions Predicted in Science Fiction.