A Mary Sue (sometimes just Sue), in fanfiction, is a fictional character with overly idealized and hackneyed mannerisms, lacking noteworthy flaws, and primarily functioning as a wish-fulfillment fantasy for the author or reader. Perhaps the single underlying feature of all characters described as "Mary Sues" is that they are too ostentatious for the audience's taste, or that the author seems to favor the character too highly. The author may seem to push how exceptional and wonderful the "Mary Sue" character is on his or her audience, sometimes leading the audience to dislike or even resent the character fairly quickly; such a character could be described as an "author's pet."

While the label "Mary Sue" itself originates from a parody of this type of character, most characters labeled "Mary Sues" by readers are not intended by authors as such. Male Mary Sues are often dubbed "Gary Stu", "Larry Stu", "Marty Stu", or similar names.

While the term is generally limited to fan-created characters, and its most common usage today occurs within the fan fiction community or in reference to fan fiction, original characters in role-playing games or literary canon are also sometimes criticized as being "Mary Sues" or "canon Sues," if they dominate the spotlight or are too unrealistic or unlikely in other ways. One example of this criticism is Wesley Crusher from Star Trek: The Next Generation.

The term "Mary Sue" is taken from a character created by Paula Smith in 1973 for her parody story "A Trekkie's Tale," published in her fanzine Menagerie #2. The character in question was Lieutenant Mary Sue ("the youngest Lieutenant in the fleet — only fifteen and a half years old"). Smith's story poked fun at unrealistic and adolescent wish-fantasy characters in Star Trek fan fiction. Such characters were generally original (non-canon) and female adolescents who had romantic liaisons with established canon adult characters or in some cases were the younger relatives or protégés of those characters. They also possessed unrealistic, often exotic skills beyond those that would have been expected of a character in that series or of a conventional author surrogate. "Mary Sue" was expanded to include any author surrogate or overly idealized character who plays a big role in original fiction as well as fan fiction.

Today "Mary Sue" carries a connotation of wish-fulfillment and is commonly associated with self-insertion (the writing of oneself into a fictional story). True self-insertion is a literal and generally undisguised representation of the author; most characters described as "Mary Sues" are not, though they are often called "proxies" for the author. The negative connotation comes from this "wish-fulfillment" implication: the "Mary Sue" is judged a poorly developed character, too perfect and lacking in realism to be interesting. Such proxy characters, critics claim, exist only because authors wish to see themselves as the "special" character in question.

The term is also associated with cliché such as exotic hair and eye colors, mystical or superhuman powers, exotic pets, possessions, or origins, or an unusually tragic past, especially when these things are glaringly out of step with the consistency of the canon. These features are commonplace in "Mary Sues", though even a character who lacks them may be labeled a "Sue" by some critics. The term is more broadly associated with characters who are exceptionally and improbably lucky. The good luck may involve romance ("Mary Sue" always gets her man); adventure ("Mary Sue" always wins a fight or knows how to solve the puzzle) and popularity (the "right people" seem to gravitate towards the character). These characters have few problems while attempting to achieve their goals. "Everything goes her way" is a common criticism regarding "Mary Sues", the implication being that the character is not sufficiently humanized or challenged to be interesting or sympathetic.

This is an article reprint. For futher reading and study, visit the original Wikipedia article.