A Mary Sue is a character the story bends around: everyone loves them, they're good at everything, and their flaws never cost them anything. This test helps you spot the signs in your OC and fix them.
The name comes from a 1970s Star Trek parody, and the male version is sometimes called a Gary Stu or Marty Stu. The label gets thrown around unfairly, especially at female characters who are simply competent, so use this as a check, not a verdict. A character can tick several boxes and still be great.
The quick test
Answer honestly. Give yourself a point for each "yes".
The character
- Are they the best at their main skill, with no one close?
- Do they have several unusual traits at once: rare eye colour, tragic royal ancestry, a unique power, a famous parent?
- Are their flaws things like "too kind", "too loyal" or "cares too much"?
- Did they master something difficult with little or no training?
- Is their tragic backstory mentioned often, but never affects how they act now?
Other characters
- Does almost everyone they meet like, admire or desire them?
- Are the people who dislike them shown as jealous or plainly in the wrong?
- In fandom roleplay, do canon characters drop their own goals to focus on your OC?
- Do canon characters act out of character to make your OC look good?
The story
- Do they win most fights and arguments without real cost?
- Do problems get solved by their special trait, rather than by effort or a hard choice?
- When they make a mistake, does it turn out to have been the right call after all?
- Do they rarely need help from anyone else?
Scoring
- 0–3: You're fine. Every protagonist has a few of these.
- 4–7: Worth a look. Pick the two that bother you most and fix those.
- 8 or more: Your partners may be struggling to find room in the story. Read on.
Why it matters more in roleplay
In a novel, a perfect hero is mostly a reader's problem. In roleplay, it's your partner's problem too. If your character always wins, always knows, and everyone adores them, your partner's character has nothing to do but watch. That's why this overlaps with godmoding and power balance.
How to fix it
Give flaws a cost
A real flaw causes trouble. "She's stubborn" means nothing until her stubbornness loses her a friend, a job, or a fight she should have walked away from. Write at least one scene where a flaw hurts her.
Let other people be better at things
Your character doesn't need to be the best swordsman, the best healer and the best liar. Pick one strength. Let your partner's character be better at something your character needs.
Make wins expensive
Every win should cost something: an injury, a secret revealed, a debt owed, a relationship strained.
Let people dislike them for good reasons
Some people should dislike your character because your character did something wrong, not because they're jealous.
Trim the specialness
One unusual trait is interesting. Five is a costume. Keep the one that matters most to the story and drop the rest.
Make the backstory matter now
If their parents died tragically, how does that show up today? A fear of hospitals, a refusal to make plans, a habit of overpacking? Character Motivation helps you connect past to present.
The opposite problem
Some writers fear the label so much that they write characters who are miserable, unlikeable and useless. That's not better. Competent, attractive, lucky characters are fine. They just need to want something they can't easily get. See Character Creation: Common Pitfalls to Avoid for other traps, and Character Arcs in RP for giving them room to grow.