It’s strange that none of my characters, even the NPC’s I run as a gamemaster, have ever been called been called Mary Sues. Part of it is because they’re usually guys, but it’s usually because the characters are fun. It’s really easy, and soon you shall know my secret.
Any time I create a character, I ask myself one simple question: Could I see that character at a bar? It doesn’t need to be an Irish pub, even though it helps; the basic question is if the person (note: “person”, not “character”) is capable of holding a conversation. Even the most obsessed psychotics are capable of holding a conversation; even an autistic can communicate their desires, albeit in limited fashion. In essence, is their something in the character that makes that character a person, with desires and wishes, balanced against their flaws and handicaps?
The problem with alien psychologies is that the writers too often ignore that even an alien psychology has to deal with motivation of some sort. It’s easy to forget that, but even an insect has a motivation, even if it is just finding the next meal and surviving. Most of the alien psychologies aren’t that alien when you analyze them from the stance of what their motivation is. There is no real alien psychology, at least, not in the since that it has no similarities to a human one.
A Mary Sue is the closest I’ve seen to an alien psychology. Think about that for a moment: There is no long-term motivation for the character, as any goal she sets is easily attained. And when she does set a long-term motivation, the obstacles that come up are easily dealt with, thus making even world peace just a few weeks away. Worse, even the flaws would only take a few sessions of therapy to deal with. Interestingly, the character may have been the victim of rape or molestation, and yet she still manages to dream about losing her virginity with a handsome man. Just once I’d like to see a Mary Sue fall for a the geeky boy that virtually stalks her…
A Mary Sue is an aberration from a writing perspective. I appreciate the fantasy nature of the aberration, yet, the character and most of her friends are usually not people that you could hold a conversation or debate anything of worth with. I bet you could at least debate Nietzsche with Darth Vader, and it would be interesting. A good writer will create the full personality of his characters; try to hold a basic conversation with one, and if you can, then the character is solid. Otherwise, try, try again. Please!