In any case, here is my take on a perennial problem:
The Care and Feeding of Mary Sues
By Kurt Wilcken
The term comes from fan fiction. A "Mary Sue" is a story in which the main character is an idealized fantasy version of the author. Veteren fan-ficcers tend to look down upon "Mary Sues" as hopelessly amateurish, which isn't exactly fair. All authors project themselves into their works and base characters on aspects of themselves. Charles Dickens did this with David Copperfield. Mark Twain did it with Tom Sawyer. Of course neither David Copperfield nor Tom Sawyer ever got to date Mister Spock.
(Some pedants have attempted to create a male equivalent for the term, such as "Harry Lou" or "Larry Q." I feel this is unnecessary. A "Mary Sue" is a "Mary Sue" no matter what the gender.)
Classic "Mary Sue" characters tend to be talented, intelligent, and charismatic. They were top of their class at Starfleet Academy. They are natural Quidditch players. They have a telepathic bond with their pet Rigellian Octo-kitty. Their breath is naturally fresh and their teeth glint when they smile.
Some RPG players I know who are also fan fic writers have borrowed the term for a gaming character who is all-powerful and uber-competent. You know the kind I mean: the Barbarian with a Dex of 18, a Strength of 27 and a Magical Sword +3 vs. Anyone Who Annoys Me; the Wizard who has every spell in the book inscribed in a Ring of Memorex; the Ninja who doesn't actually have to go on adventures because he has an army of animated shadows to do his bidding for him. Usually we call them Power Gamers.
So why didn't I say so in the first place? I suppose because Power Gamers have a certain innate coolness. Nobody likes someone else who is a Power Gamer, but when you're the Power Gamer, why that's something else entirely. Try this experiment: Stand in front of a mirror, look yourself in the eye, and say in a loud, clear voice: "I am a POWER GAMER!!! Fear my dice! Bwa-ha-hah!!!"
Felt good, didn't it?
Now try standing in front of the mirror and shouting, "I am a MARY SUE!!! Fear my dice! Bwa-ha-hah!!!"
It just isn't the same.
(Oh, and don't try this experiment unless you're sure your parents, significant other or non-gaming friends can't observe you doing it. They Won't Understand.)
(Too late? Oo. Hard cheese, old man.)
So, what should GM do who finds himself dealing with a Mary Sue? There are several options. The most obvious option is to DRAW BATTLE LINES.
I briefly played in one group where the GM had a sign in her gaming room reading "The DM's Word is Law." She declared that her games would be run strictly by the book and that she would put up with no attempts to bend the rules. The end result, of course, was that her players became consummate rules lawyers and would get into arguments with her over said rules.
My wife Lute and I entered her D&D game with first-level characters. All the other players were 8th Level or higher, and we often found ourselves standing to the side while the tougher characters fought the monsters. One of her players, a friend of mine who brought us into the group, was playing a 10th Level Assassin with a small entourage of followers. This was the kind of player who justified everything he did by saying "I'm just playing my alignment" and if questioned would claim that he was the only one who truly played the D&D alignment system correctly.
The higher-level members of the party encountered a big-time boss monster. In the ensuing fight, the monster struck the Assassin with a +4 Hammer of Irresistable Force or some such thing. The GM rolled a Critical Success, which under normal circumstances should do the target some serious ouch. The Assassin, however, announced that he was wearing his Helm of Utter Invulnerability and therefore took no damage.
"You took a Critical Hit!" the GM argued, "Of course you took damage!"
"The Helm of Utter Invulnerability protects the wearer from all damage. It says so in the book. I have it on my character sheet."
The two of them argued back and forth for a good fifteen minutes. It might not have harmed the Assassin, but it sure killed the game.
So direct confrontation is not always the answer. A better approach might be to CHANGE THE RULES.
My buddy Fredd tells the story of the first D&D game he ran. His brother and his friends had developed a system for dealing with dragons. First the magic-user of the group would send an illusion of the party into the dragon's lair. After the dragon had wasted it's breath attack on the illusion, the party would rush in and attack.
So Fredd had the party come across a red dragon snoozing in a dungeon. As usual they sent an illusion ahead of them. The dragon opened one eye and said, "Do you think I'm so stupid that I don't know an illusion when I see it?"
The party had to think for a change. After some discussion, they tried a direct attack. The dragon breathed his firey breath on them and the party managed to dodge the worst of the attack. Now, they thought, they could attack the dragon safely.
"Goodness me! The dragon said, "I've used up my breath attack! The only thing I can do now is... use my OTHER breath attack!!! RARRRR!!!"
"That's no fair!" the players complained. "That dragon only gets one breath attack per day!"
"I'm special!!!" the dragon roared.
The party wound up running out of the dragon's lair, but to their surprise the dragon followed them. He couldn't squeeze through the dungeon passages very well, and the party could easily out-run him, but he kept after them. Every time the party paused to rest, they could hear the dragon down the hall yelling, "Come back here ya little gits!" (Or he might have called them something that rhymes with gits. It was something like that). In any case, the encounter challenged their expectations and resulted in a game more enjoyable to everyone.
Fredd had one cardinal rule for dealing with Mary Sues: when a player asks for something you think is unreasonable, LET THEM HAVE IT. And then let them deal with the consequences.
In one of his games, a player wanted to be Elric of Melnibone, the classic Michael Moorcock character. Fredd temporized. "You can be someone like Elric." "Can I have a sword that sucks the souls of it's victims?" "Okay, okay."
So "Elric" got a magic sentient sword that could devour souls. And it talked to him. "Feed me, Elric," the sword would say in the voice of the plant from "Little Shop of Horrors", and it would tell him who to kill: the minotaur around the corner; the band of orcs waiting in ambush; the harmless NPC peasant he met in the road. With a good role-player, this could have led to some interesting character conflict as he struggled between his conscience and the demands of his bloodthirsty blade. As it was, our Elric just did what the sword told him to. Before long, half the party was ready to kill him.
In another game, one of his players thought it would be cool to play a vampire. "I'm gonna be one of the Lords of Ravenloft!" he boasted. "But I thought under Ravenloft rules once you become a Lord you're automatically an NPC," I said. "Oh, Fredd said it's okay." I caught a glimpse of Fredd's evil smirk and knew he had things well in hand.
So the guy got to be a vampire. He got his cool vampire powers. He got to enslave a hot vampire babe to his will, (woo-hoo!). He got a castle and hunchbacked minion named Igor. And after a couple months worth of games adventuring with the party, Fredd decided to give him some consequences too.
The gods appeared to the vampire and informed him that because of all the Good Actions he had been performing with the other adventurers, they decided to reward him by removing his curse. All of a sudden, his cool vampire powers were gone, Igor was planting flowers around the castle and worst of all, his sexy vampire babe had become modest and virtuous! "Nooooo!!!!!"
The game Teenagers From Outer Space has a special rule for Power Gamers. "Like real life we reward mediocrity by grading on the curve." Anyone who tries to overload his character's attributes and abilities risk invoking the Too Much rule. At the start of play, the GM arbitrarily chooses a number. If anyone succeeds in a roll by that amount or more, he is deemed to have succeeded by Too Much. He gets what he wants, and then some. He succeeds in impressing the cute girl from Vega Epsilon, but now she's so enraptured by him that she won't leave him alone. He succeeds in beating that rich kid in a thumb-wrestling tournament, but now the kid is sending his ninja minions for vengence. He succeeds in training his Arcturian Mega-puppy for the dog show, but now the dog is more famous than he is. Success brings its own problems.
Which brings us to perhaps the most satisfying way to deal with a Mary Sue, which is to MOCK HIM. Power Gamers tend to take themselves very seriously. Sometime a little embarrassment is just the thing to teach them to behave. If nothing else, it will entertain the other players who probably have been just dying to see the jerk get his comeuppance.
My wife, Lute, was in an online game once with a particularly annoying Mary Sue. Online games tend to be a blending of RPs and fanfics; they generally lack hard and fast rules and often lack GMs to moderate them and so they tend to be fertile grounds for Mary Sue-ism. In this case the fellow had a bad habit of jumping in and commenting or acting on everybody else's posts, even if his character was supposedly someplace else. In annoyance, Lute changed him into a platypus. It was weeks before she got around to changing him back. Ever since then, every time that player has gotten out of line, she threatens him with becoming a platypus. Incredibly enough, the guy has become resigned to the fact and even puts it in his online sigfile.
If I had been the GM in the situation with my friend the Invulnerable Assassin, I probably would have conceded that his helm did protect him from all harm... but that the Critical blow from his opponent had driven him into the floor like a tent peg. Then I'd let him figure out how to get out. But then it's always easy to be the Monday Morning GM.
But having said all this, the GM has to keep in mind that the most important thing is to have fun. We all game to enjoy a bit of wish-fulfillment and so to a certain extent all RPG characters are Mary Sues. The only time Mary Sues absolutely have to be dealt with at all is when they wreck the GM's plot and interfere with the enjoyment of others and even then, the latter event is more serious than the former. With proper care and tending, even a Mary Sue can be a constructive part of an entertaining game.
Fear my dice.