Today, I will talk about a trope that any good writer would tell you to avoid like the plague.
It is the Mary Sue.
A Mary Sue is a character who is overly perfect. That is she or he (male examples are know as either a Larry Stu, Gary Stu, or Marty Stu) has no real flaws, has any talent, and is loved by most characters. If a character does not like them, even if they have a real reason to dislike them, said character will be depicted as extremely unsympathetic if not evil. The plot bends over to facilitate the Mary Sue, and the Mary Sue is so unrealistically perfect to the point, that they are not a real character: they are nothing more than a personification of ideals.
While such characters have existed for as long as people have been telling stories, the term was first coined in 1974. Back before the Internet, fanfiction was written by hand or on typewriters, exclusively. Some fans would hold conventions where they would distribute the fanfiction they wrote in fan magazines. One of these fan magazines was called Menagerie, and it contained a Star Trek fanfiction called A Trekkie’s Tale.
A Trekkie’s Tale was about a fifteen-year-old girl named Mary Sue who becomes a lieutenant on the Enterprise, saves the crew, and dies from her injuries. It was written by Paul Smith who wrote it as a parody of fanfiction stories where the writer would create a character based on them and make them unrealistically idealistic.
The term caught on and was used to describe all sorts of characters that are perceived to be implausibly perfect. However, not everyone agrees on Mary Sue traits or even if a given character is a Mary Sue. But one thing is certain, a Mary Sue is not a good character trait, and even if one wants to create an idealistic character, they should still make them realistic, flaws and all.