Mary-Sues: Writing Realistically. . . According to the Universe
I'm sure I've told you that you have to be as realistic as possible in order for your character to seem, well, real. Believable. Three dimensional. Someone who can practically pop out of your writing or comic and interact with you. The truth is that was half of an exaggeration. Yes, be real, but only as real as the universe it takes place in is. If the universe is more manga-esque or cartoony where the average female can punch a burly person sky-high, and you create a character who doesn't do anything of that sort, or if you as the creator think you can't do that, then your character can become quite plain because you'll restrict yourself. Basically, be as real, or as loose, as the universe is.
If you're a person who constantly makes the, "This is totally unrealistic" comment when reading a story, especially in fan fiction, there is probably a reason for it, and shouldn't be docked down points until all of the attributes are observed.
Realism vs. The Universe
One of the biggest complaints I've read that I've even noted about it as well, are women's breast size. As silly as that is, this one thing raises so many red flags that the female character may be a Mary-Sue. Female characters, especially the more important characters, in original stories or fan fiction, can't have sexual appeal or be endowed in the chest area? Moreover, who's to say that having big breasts are even sexually appealing? (I'm not a guy, so I probably wouldn't understand it even if a guy explained it to me.) I also explained in "Things You Need to Know" that physical description shouldn't matter too much as long as there is some reason behind it. In that part, I said, "They only become MS traits when it's without reason, like having big boobs when the character is only thirteen"; however, if the universe's thirteen year olds have a DD chest naturally, then you can certainly make your character have a large chest without it having fingers pointing at her. Or him if that's how the universe works.
In the Naruto fandom, there are fans that have made female characters, and many of them do have larger than B cup breasts. As much as an inconvenience to having large breasts are to a female ninja should, it's genetics and hormones in food that give them that size, so it's not the character's fault. Besides, you don't hear Tsunade, the biggest breasted ninja around, complaining about her assets. She doesn't even bind them or wear a bra (are there even bras in Naruto?) In fact, you don't hear any of the female characters complaining about their chests!
Also in Naruto, even though the majority of these characters are fighting during their missions, they don't wear much armor, and yet those who make fan/original characters without armor get the brunt end of the Mary-Sue Killers for not being real enough. The most armor I've seen on the average canon character are the clothes on their backs, their headbands, and a vest if they've earned that rank. That's it. No one wears flexible chain mail, helmets, some wear kneepads and elbow pads, and only a few wear leg or arm plates. Yet the fans that make characters for their stories have to think about armor in order for their character to seem realistic? If you want more realism in something like this, complain to the creators, not the fans who imitate what they see.
Even the character's background stories, and how it affects the character's personality, can be unrealistic in some universes according to certain psychological studies. Have you really ever met someone who was so shy that they actually fainted (on more than one occasion) whenever the person he or she liked talked to them? Or, a person who seemed to be on a constant sugar-high with no crash? How about someone who has a patience of a saint, and never ever seems to get mad, even in the most frustrating of situations? It's fun to compare your friends to these kinds of characters, but you'll realize that you haven't really met anyone with those kinds of personalities. None of these examples is realistic character personality traits, and yet used in animated shows. Granted, those characters aren't like that one hundred percent of the time, but are like that most of the time. They are fictional cartoons and aren't supposed to be taken seriously, so writing in those kinds of universe, fan fiction or original fictions, should be looser, than realistic, depending on what kind of story you're writing.
Of course, all of this would also work the other way around. You wouldn't see a guy able to survive on the moon without the space suit on in the real-world kind of story. If you wanted to write in a historical, realistic, universe, then you definitely need to do your research. Japan, where there would be ninjas, you would have to do extensive research on the clothes, weapons, and why they needed ninjas. Unbelievably, kunai knives weren't made to be thrown, and ninjas can't disappear in a puff of smoke. They were more spies than assassins. Guns in the US civil war era were wildly inaccurate, hence the saying, "Don't shoot until you see the whites of their eyes," otherwise it was just plain luck that someone actually hit someone at a farther distance. There are Native American tribes who honor homosexual people and called them two-souls because they had both the feminine and masculine aspect in their soul. I could list on and on that even some realistic historical fiction overlook them, but I think you get the message.
In realistic fiction, you have to stick with the facts. Period. In unrealistic fiction, do what Mark Twain said, "Get your facts first, and then you can distort them as much as you please." In addition, even though fan fiction is based on already published media, the fans still have to study whatever the universe they're going to be writing.
I've said before that Mary-Sues are often unrealistic in one way or another, but are they Sues only because of the universe it takes place where, in actuality, they fit in? If so, then the character you're calling a Sue isn't a Sue. The character is just unrealistic when compared to the real-life universe.
When is a Character or Story "Realistic"?
Basing on what the universe is like is the question of realism. The universe is the base, the soila fictional "Earth". The story is the tree, and the characters are the leaves. The universe itself has to have a type of environment that's balanced. What's the history? How much pollution is there? Is it mostly rainy, or is it dry? What are the communities like? Are there any major religions? What are the taboos and superstitions like? How does all of this and more affect what's happening in the present? Does this affect the story or the characters?
The last question's answer should be an obvious 'yes'. The universe, no matter what it is, will always have an affect on the story and characters.
Study how the world in which you create, or whatever was created, works, and then work on the plot. What's the villain planning, and how will it be stopped? How does the guy get the girl (or guy if he swings that way)? What is your idea of a good story? Work out a timeline or something. After you at least have a basic idea of what you want to happen, work on the characters (refer to "Things You Need to Know"). Balance the universe, the story, and the characters. Once the tree is in full bloom, the fruit will grow, telling you that your story is good, and "realistic", no matter how many physics laws are broken in your universe.
As long as you think your story's good, that's all that really matters, but it doesn't hurt to listen to a critic occasionally, especially when it doesn't make sense from the reader's point of view. You as the creator know all of the answers, and so leaving the readers clueless even after the ending is bad. If you can't fit a major detail in the story, and it's an important detail, that tends to be a bad sign. Don't write the story with plot holes and missing information, even if you plan to write a handbook for the book/series. Even if it's tiring, and boring, think of your readers. The details and explanations, no matter how mundane, are important to someone. It's better that it be in the story itself than in a handbook.
If everything in the universe, the story and your characters are explained, it's "realistic" enough.
When the Real-Life Universe Isn't Real Enough
If the otherwise fictional story takes place in the real-world universe, then the laws of physics have to be followed just as the characters have to be limited to being realistic. This still especially applies when the story is claiming to be the real-world, even when there are additives to it (i.e.: magic, vampires and werewolves, monsters, and other fantasy and superstition inspired fiction).
Because I am tired of picking on the House of Night series, I'm going to pick on the Twilight series by Stephenie Meyers, merely because it serves as a better example.
The Twilight universe is set in the real-world with the addition of vampires, werewolves (although none actually made an appearance), and shape shifters (the werewolf wannabes). I have read the four book series, not including the story of Bree, I have looked through the handbook guide, and it was merely mindless entertainment. I liked reading it, I just wouldn't read it if I wanted to read something more serious and in depth. Moreover, I'm not even going to bother reading the series from Edward's perspective that Meyers is supposedly working on. The story had marvelous conceivability, an original twist on the vampire mythology (despite that a lot of people despise the sparkly attribute), good potential in the villains, and, despite it seemingly a cliché idea, what would have been a great love triangle, except that Meyers could not execute the story at all well. At some parts it was obviously tried too hard and other parts there wasn't enough trying.
The universe wasn't at all the bad partit was practically our world anywayit's just that the story wasn't fleshed out, the characters were ill-described whether actually describing them through adjectives, or describing them through action, but what really killed the story was the writing style, mostly because Meyers made her characters separate pieces of stereotypes.
Edward Cullen, the vampire heartthrob, acted like he hated Bella in the beginning, spied on her when she was sleeping for months, and probably followed her around most of the twenty-four hours in a day before he told her he was watching her. He dumped her on various occasions for his own reasons without hearing her out, got extremely jealous when other guys were in the picture with Bella, all the while villainizing himself just because he's a vampire and that he's killed people before. Despite all of that, Bella thinks he's the perfect gentleman and loves him.
Jacob Black, the thought-to-be-werewolf-but-actually-a-type-of-shape shifter, is the seemingly perfect boyfriend: cute, cuddly, into cars and mechanics, and actually cares, despite all of the stolen kisses because he knows that Edward is practically carrying a picket sign saying "I'm emotionally abusive and am self-absorbed" and Bella, the one he initially loves, is suffering. However, Bella just manipulates him for information, emotional support knowing his feelings for her, but didn't tell him that it wouldn't work out between them that way from the beginning, and just used him for her own gratification. Then, as if it's supposed to erase all of his heartache, he imprints with Bella's daughter. Therefore, overall, Jacob Black is just a pushover.
Then there's Isabella "Bella" Swan, the human who has no interest in other human beings, so just ignores the people who immediately befriend her. She criticizes herself constantly, calling herself either too plain or too ugly, despite all the people in her life telling her that she's beautiful, or the fact that people had taken an immediate interest in her, and is overall defenseless and weak in the physical aspect as well as socially and mentally. She also manipulates people, including Edward in order to gain a sexual favor (though it didn't work on Edward), for her own benefit. Basically, Bella is an overly lovesick, damsel in distress, teenager.
Since most of the story is in Bella's perspective, you can probably guess how badly the story would be. So much self-angst, self-criticism (which all too suddenly disappears as soon as she awoke as a vampire), and romance, with not nearly enough action especially when there were supposed to be fighting scenes because Edward didn't want to put her in the line of fire. A pathetic attempt at mental cracking in the form of hearing her beloved's voice every time she did something dangerous, and a love triangle that wasn't at all a love triangle because all she ever thought about was Edward, and becoming a vampire. All of this affects the overall writing style, so it's average; something you would find on preteen writing sites. Also, some of the more supposedly powerful villains weren't powerful at all. Victoria was the real threat. James was just the spark, and Laurent became a chew toy. Not even the Volturi, the oldest vampires in existence, who set up the rules and enforced them with the help of the chosen vampires with special abilities, were even real villains. They were just a broken record of threats.
Then there's the overall writing style. If you haven't figured it out, the description between characters, action were mediocre at best, but there was better description in the setting. Interactions between characters were either in the range of hardly having any important interaction, to super cheesy, as if you were watching one of those 1920's romance films with over rehearsed lines, as if just one sentence would make all the years of hurt just disappear. I appreciated the use of a thesaurus; however, Meyers overdid it a lot with words hardly anyone uses, especially not a sixteen-year-old girl.
The universe is solid because Meyers hardly changed it. There is a tree, but it's in the middle of rotting because there's so much she could have done with the plot, but didn't. There are hardly any leaves at all, and they are brown and cracked because only a few characters were developed, but the writing style was filled with exaggeration and euphemisms that it made even the more decently described characters bad. Even with all of the potential the books had, there are no fruit, unless you count that Meyers earned millions of dollars on this story and is now rich beyond all reason, then money would equate to fruit. Therefore, because of these errors the story and characters are deemed unrealistic in this real-life universe, and would make the entire story Mary-Sue.
Although, in the example of the Twilight series, I don't think that the characters are Mary-Sues per se, because if they were stripped from the story and the writing style, then they are all balanced, it's just that the priorities are skewed in terms of interaction between characters in the plot, and there's a major issue with the overall writing style. The main problem was the writing style, and that ruined the story.
In conclusion, there are times when realism is called for, and other times where you have to write in a more loose style. If you keep restricting to the safe-zone of absolute realism, despite how hard it is writing in a realistic way when constantly questioning yourself if something is real or not, you'll have a tougher time writing in looser kinds of universes where the realistic physics laws are often broken, whether for fantasy or comedic purposes. Readers, you too need to read in both styles so you can tell the difference between realism, and the fact that most fiction does not take place in a realistic universe, so most characters shouldn't be called Mary-Sue or Gary-stu because of the universe their lives takes place in.