Mary Sue , alternatively written as marysue, is a negative term to refer to a particular type of flawed original character. Although the word is a name, the term is not, and correspondingly, it is generally not capitalized. Mary sue is a gender neutral term, but some use the term gary stu to refer to male characters of this type.

A mary sue is an idealized character who the author has over identified with. Mary sues have appearances and skills their creators like, which is why individual mary sues vary based on the author. The basic canon, or reality of the universe, will be altered to allow the mary sue to have these traits. In a similar vein, the story will revolve around the mary sue to an excessive degree, even more than their main character role would normally cause. Although some mary sues can be relatively well developed characters, their supporting cast never is, and most other characters exist to talk about the mary sue, with the good characters defined as the ones who talk positively about her, and the bad characters defined as those who are cruel to or jealous of her. The most extreme example, sometimes used as a one-question litmus test, is the commonplace scene where characters express sympathy and amazement over something bad that happened to the mary sue, even though their own experiences have been far worse.

Although the stereotypical mary sue is often perfect in various ways and has a number of impressive abilities, these are merely common features, not a true trait of a mary sue itself. Technically-flawed mary sues are possible, even common, with typical problems being scars, isolation and abuse, clumsiness, a "fiery temper", failing to take things seriously, or an inability to do something unimportant (such as a bad singer or cook). Mary sues do not have any flaws that their creators consider negative. As such, flawed mary sues may be bony and made fun of for it, or actually have anorexia, they will rarely be overweight.

In pokemon fanfiction, female mary sues generally have long hair of a color other than brown, with black, silver and blue being among the most popular. Their eyes are more varied, although again rarely brown, although they usually run along certain patterns in connection to hair, such as red-haired characters having green eyes, and black haired characters having icy blue eyes. A mary sue trainer will almost always get a starter who has one or more of the following traits:

  • Larger than normal
  • Unusually colored
  • Not a standard starter (or not a standard regional starter)
  • Unusual ability (speech, ability to use unusual moves)
  • Significantly stronger than normal
  • Eevee