Here's a second installment! I wasn't originally intending to write more, but what can I say? I was struck by inspiration.
And thanks to all who reviewed/will review! Thanks to you, I now know that purple eyes really are possible (albeit rare) in real life. You learn something new every day!
--theweirdperson
I. They are "fated" to do something.
Example: Rhonda looked up at the stars, contemplating her destiny. A prophecy written two thousand years ago had spoken of her, and how she would be the only one who would be able to save the world from an enormous threat...
If you're trying to make your character fit in with the X-men/Brotherhood/Acolytes/Whoever, trying to make them more important will not help your cause, and frankly, it sounds silly. The only canon character who came close to this was Rogue, but the golden rule of OCs is that canon characters will always meet with more acceptance than yours. Why? Because they come from the creators of the show, rather than a random fanfic author.
J. If they're evil, it's for a good (or at least sympathetic) reason, AND any heroes trying to stop them act like jerks while doing it.
Example: Mordeo held the pendant in his hand. It was the key to saving his sister... but it would also depower all mutants. But it was mutants who had killed his sister, it had been those "heroes", the X-men, who had destroyed her. The only way to bring her back was to activate the Kryon gem of the amulet at noon on the summer solstice...
"Stop right there, loser," yelled Cyclops. Mordeo turned to face him.
"I'm doing this to save my sister," Mordeo said.
"Oh, you mean that chick we eliminated?" scoffed Jean. "She's hardly worth saving."
"Arrrgah!" yelled Mordeo, transforming...
I'll bet you thought that being a villain automatically exempted your OC from Mary Suedom. Wrong! Even a villain can be a Mary Sue.
While villains usually have a reason for doing what they do that the audience can sympathize with (such as the fact that Magneto has faced persecution in the past and wishes to spare mutants from the sufferings he endured), when the heroes start looking more like villains, it's likely that you've created a Villain Sue. Sure, the X-men might let off a snide remark or two while fighting, but if you've twisted them to the extent that the reader can't tell who's the villain and who's the hero, you have a problem.
However, simply being evil for sympathetic reasons is most certainly NOT a sign of being a Mary Sue-- it is a sign of a well rounded character. Just wanted to make that clear.
K. They expose the 'flaws' of a canon character whom the author personally dislikes.
Example: "Wow, I never realized that Scott was such a jerk," mused Jean.
"Yeah. I guess I was taken in by his guile," Rogue said softly. "Thanks, Micah."
"It's no problem. My soul-sight lets me know what people are really like, and I didn't want you to get burned," Micah said somberly.
Do canon characters have personality flaws? Yes.
However, most people with whom said character is closely acquainted with will already know about these flaws, and have learned to live with them. This ties in with J-- to pull it off, it would require you to warp the personality of a canon character to make them evil enough.
L. They aren't human. Or a mutant. They're secretly an elf/god/vampire/fill-in-the-blank.
Example: Kiana brushed back a strand of golden-blond hair behind a pointed ear. She knew that she had to keep her origins secret-- if anyone knew that she was an elf-naiad hybrid, she might be hunted down and destroyed, just like her parents had been...
As far as I know, there are no mythical species in the X-men: Evolution universe. Making your OC an elf/god/vampire/fill-in-the-blank just to make them 'cool' is definitely stretching it. If they're a half breed, it goes double (especially if they angst about being an outcast from both their parents' people).
This rule can be relaxed if you're writing a crossover, and the other universe you're writing in does have elves and such.
K. They're older than Wolverine, Mystique or Apocolypse.
Example: Haknat-panuut strode boldly toward the town of Bayville. Nowadays, he was calling himself Paul, because Haknat-panuut isn't nearly as common a name as it was 5000 years ago.
That has to be some killer mutation if it allows one to survive for millennia. But having that sort of mutation is a point against an OC if they don't wish to be categorized as a Mary Sue.
L. They're related to one or more canon characters (despite never being mentioned on the show)
Example: Sheila ran towards Wanda, Pietro, Rogue, and Kurt. "Hey! I'm the lovechild of Mystique and Magneto, so that makes you all my siblings! Isn't that great!"
Attatching your OC to a canon character whom you particularly like is rather unrealistic. If they really had another sibling/cousin/other, wouldn't they have been mentioned on the show?