The term "Mary Sue" comes from the name of a character created by Paula Smith in 1973 for her parody story "A Trekkie's Tale":15 published in her fanzine Menagerie #2. The story starred Lieutenant Mary Sue ("the youngest Lieutenant in the fleet — only fifteen and a half years old"), and satirized unrealistic Star Trek fan fiction. Such characters were generally original female adolescents who had romantic liaisons with established canonical adult characters, or in some cases were the younger relatives or protégées of those characters. By 1976 Menagerie's editors stated that they disliked such characters, saying:
Mary Sue stories—the adventures of the youngest and smartest ever person to graduate from the academy and ever get a commission at such a tender age. Usually characterized by unprecedented skill in everything from art to zoology, including karate and arm-wrestling. This character can also be found burrowing her way into the good graces/heart/mind of one of the Big Three [Kirk, Spock, and McCoy], if not all three at once. She saves the day by her wit and ability, and, if we are lucky, has the good grace to die at the end, being grieved by the entire ship.
"Mary Sue" today has changed from its original meaning and now carries a generalized, although not universal, connotation of wish-fulfillment and is commonly associated with self-insertion. 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 as a poorly developed character, too perfect and lacking in realism to be interesting.
The "Mary Sue" concept has drawn criticism from feminist writers.
In chapter four of her book Enterprising Women, Camille Bacon-Smith includes a subsection on the "Mary Sue" concept. While not denying that such characters exist (and offering psychological observations as to why "Mary Sues" exist), she observes that fear of creating a "Mary Sue" may be restricting and even silencing some writers.
Smith quotes an issue of the Star Trek fanzine Archives as identifying "Mary Sue" paranoia as one of the sources for the lack of "believable, competent, and identifiable-with female characters." In this article, Cantor interviews her sister Edith, also an amateur editor, who says she receives stories with cover letters apologizing for the tale as "a Mary Sue", even when the author admits she does not know what a "Mary Sue" is. According to Edith Cantor, while Paula Smith's original "Trekkie's Tale" was only ten paragraphs long, "in terms of their impact on those whom they affect, those words [Mary Sue] have got to rank right up there with the Selective Service Act." At Clippercon 1987 (a Star Trek fan convention held yearly in Baltimore, Maryland), Smith interviewed a panel of female authors who say they do not include female characters in their stories at all. She quoted one as saying "Every time I've tried to put a woman in any story I've ever written, everyone immediately says, this is a Mary Sue." Smith also pointed out that "Participants in a panel discussion in January 1990 noted with growing dismay that any female character created within the community is damned with the term Mary Sue."
However, several other writers quoted by Smith have argued that in Star Trek as originally created, James T. Kirk is himself a "Marty Stu," and that the label seems to be used more indiscriminately on female characters who do not behave in accordance with the dominant culture's images and expectations for females as opposed to males. Professional author Ann C. Crispin is quoted as saying: "The term 'Mary Sue' constitutes a put-down, implying that the character so summarily dismissed is not a true character, no matter how well drawn, what sex, species, or degree of individuality."
Marty Stu or Gary Stu is a male variant on this trope, which shares the same wish-fulfillment aspect but tends to describe a character with traits identified as stereotypically male. The Star Trek: The Next Generation character Wesley Crusher was called a Marty Stu by the feminist popular culture magazine Bitch. There is speculation amongst fans and academics that Wesley was a self-insertion character for Gene Roddenberry. Other variations include Gary Stu, Larry Stu, Mary Joe, or Marty Sam.
Further variant names have been suggested based on the specific personality of a Mary Sue, such as Einstein Sue (a highly intelligent character), Jerk Sue (a short-tempered character who lashes out), or Sympathetic Sue (an angsty character who wants the reader's sympathy).
More than one commentator has analyzed the Buffy the Vampire Slayer episode "Superstar" as being a deliberate satire of Mary Sue/Marty Stu type of stories.  In the episode, previously peripheral character Jonathan Levinson is suddenly the smartest, strongest and most well-liked person among all the other characters (even loved worldwide). Ultimately, Buffy and the other characters discover that Jonathan has performed a spell to get everyone to like him better.
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- Smith, p. 110. A footnote states this was reported to her by Judy Chien, who attended the panel at MostEastlyCon 1990 in Newark.
- Smith, p. 97.
- Smith, p. 98.
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- Kukkonen, Karin; Klimek, Sonja (2011). Metalepsis in Popular Culture. p. 96. ISBN 9783110252781.
- Carroll, Shiloh. "Psychology of a "Superstar": A Psychological Analysis of Jonathan Levinson". Slayage Online.com. Retrieved June 26, 2015.
- Wilcox, Rhonda V.; David Lavery (February 25, 2002). Fighting the Forces: What's at Stake in Buffy the Vampire Slayer?. (via Google Books) (Rowman & Littlefield).