Before You Go Declaring Other Peoples' Characters Mary Sues...

Note: The concept of a "Mary Sue" is outdated and fraught with problems, and it's time to move on to a better way of looking at things. This article is here for reading purposes only. Please see "Does My Character Work Okay?" - How To Tell For Yourself! for character advice.

Or, "how to tell the difference between genuine Mary Sues and characters you just don’t like" or "The Anti-Mary Sue Litmus Test," because way too many people have been labelling characters Mary Sues right and left for no other reason than they just don't like the character

First, if the character is female, imagine if a male character took the alleged Mary Sue’s place and did everything the alleged Mary Sue did. Would you still perceive the character as a Mary Sue? Unless the character’s actions should reasonably have negative consequences in-universe yet don’t (eg, a female character does things that would realistically end up with her getting a death sentence in that particular time period/universe), the character probably isn’t a Mary Sue; you’re probably just sexist.

If the character you suspect to be a Mary Sue is one half of a ship, ask yourself:

• Was the ship only possible because the other half behaved in a manner inconsistent with previous characterization, with any required character development not shown or poorly-shown - eg, a philanderer suddenly becomes completely faithful, never giving a thought to anyone else because the love interest is just that special?
• Does the other half of the ship ignore or give up prior friends, interests, goals, and responsibilities, becoming solely focused on the new love interest, and this is never treated as or shown to be a problem?

If you’ve answered “no” to both, then the character is not a Mary Sue for being in a relationship. Contrast Bella Swan: as soon as she meets Edward Cullen, she becomes his life.

If the character you suspect to be a Mary Sue is a fan/new character who associates with canon/old characters in any other capacity, ask yourself:

• Was it only possible because one or more of the characters behaved in a way inconsistent with previous characterization - eg, characters who would normally be cautious trust the character instantly?
• Does the canon character completely ignore other friends and associates to be with the new character, and this is never shown to be a problem?
• Is the character rude, inconsiderate, insubordinate, or even cruel to the other characters, yet never suffers any negative consequences or repercussions for it, particularly when others have?

If you’ve answered “no” to these questions, then the character is not a Mary Sue for associating with canon/old characters.

If the character is exceptionally powerful or talented, ask yourself:

• Does the character work in a profession that realistically, would require exceptional skill? (You wouldn’t expect one of the President’s personal guards to be a lousy marksman, nor would you expect an Olympic gymnast to be clumsy, nor would you expect a NASA rocket designer to be bad at math.)
• Does the character still face meaningful challenges? Does the character still have to make choices that impose very real consequences? Does the character grow or change in some way because of their choices or the consequences of their choices?

If you’ve answered “yes” to the above, then the character is probably not a Mary Sue because xe is powerful. Contrast Bella Swan after becoming a vampire: she frequently chooses options that are presented in-story as having potentially dire consequences, but these consequences never play out. Her powers aren't attached to any real responsibility, either - all they do is make life easy and conflict-free for her.

If the character has a tragic and/or traumatic backstory, ask yourself:

• Is the level of trauma proportionate to the universe the character is in? As The Hunger Games is set in a dystopian future, it's reasonable for characters to have severely messed-up backgrounds - being shot for stealing food is something that might reasonably happen. My Little Pony: Friendship Is Magic, on the other hand, takes place in a much nicer world - you wouldn't expect a guard to shoot a filly for stealing an apple.
• Is the backstory used primarily to lay foundation for who the character is now? Or does it primarily serve to make the character an object of pity and/or admiration?

Tragic and/or traumatic backstories can be vital for a character. When used right, they set foundations for who a character is. For example, Tony Stark's experience with the Ten Rings in the Iron Man film was what prompted him to make the transition from a selfish and spoiled brat to a man who, while still childish in many ways, started putting the needs and lives of others before himself. A Mary Sue will have a tragic backstory mainly as a cheap grab for attention through pity and/or admiration.