Mary Sue

A Mary Sue, sometimes shortened to Sue or  'Sue, is a type of character in a work of fanfiction that exhibits many cliched characteristics. Often she is the idealized version or self-insert of the author, who is consequently called a Suethor. A Mary Sue is often portrayed in overly idealizes ways, lacks noteworthy or realistic flaws and primarily functions as a wish-fulfillment.

Calling a character a Mary Sue is rather subjective. Often a character is called a Mary Sue because she has certain characteristics such as oddly colored eyes or hair and a bizarre name. A good writer, however, could pull off creating an original character with Mary Sue characteristics that is not a Mary Sue. The most true indication of a Mary Sue is that she changes the focus of the canon characters so that their whole reason of being revolves around her.

Etymology
Add history of Mary Sue

Sub-concepts of Mary Sue
There are many different varieties of Mary Sues, all with different strategies for getting control of the story: Emo!Sues, Bubbly!Sues, Goth!Sues, Evil!Sues, Possession!Sues, and many others.

Gary Stu
The male version of a Mary Sue is sometimes called a Gary Stu or a Marty Sam.

Litmus tests
Various tests have been written where authors can test their original characters on their Sueness.