Mr. Dustmop, OC's, and Sue/Stu characters

In the latest chapter of my fic, we met an OC by the name of Dustmop, an elderly unicorn janitor who was called out of retirement to get Star Swirl's library into shape for its new owner. To be honest, I was a little nervous about including an OC in this story, especially considering a lot of OC's for MLP fanworks are either author avatars, cheap clones of cannon characters, or the offspring of shipped characters that if one takes a moment to think about would never happen (IE-an OC that is the offspring of Celestia and Discord for instance). The result is a Mary Sue/Gary Stu character that completely ruins the story.

Now let's take a moment and discuss what makes a Sue/Stu character. Contrary to popular belief, Sues/Stus appear not only in fan works but original works as well where they are known as Canon Sues/Stus. (Some of the more insufferable Cannon Sues/Stus I've seen are Bella Swan from Twilight, the titular character from Suzuka, and Rand al'Thor from the Wheel of Time). But what is it that makes a Sue/Stu character? The common belief is that Sue/Stu characters are always awesome at whatever they do, are flawlessly attractive, and can do no wrong in their actions. But is this really what makes a Sue/Stu? I've seen characters who were these things and more and yet were still likable and relatable because in the end, they existed for the story rather than the story existing for them. To me that is what defines a Sue/Stu character.

Going back to Dustmop, while I can't predict how my readers will respond to him, I hope at least they'll grant me a chance to flesh out both him and his role in the story. In time, more will be revealed about him and his connection to what's going on in both Prime and Mirror Equestria. Although, I'm sure some of my more observant readers have already figured it out from the clues I've already left.

...To be continued.