Mary Sue defined:
Mary Sue is a pejorative term, sometimes shortened to Sue, used to describe or criticize a fictional character that exhibits some or most fan fiction clichés, making the character itself something of a cliché. The term "Mary Sue" is often considered unisexual, although masculinized variations such as "Gary Stu" or "Larry Sue" are frequently used in reference to male characters.
What a Mary Sue is:
Exactly what makes a character a Mary Sue is subjective, although commonly accepted criteria include the character being exceptionally lucky (romance, adventure, and popularity with the right people seeming to gravitate toward the character) and having a role in the story that upstages the other characters. Some believe that if a character is unusual or remarkable in some way, then the character will immediately be perceived as a Mary Sue. Others agree that "Sue traits" are cumulative; most characters have "Sue traits" to some degree, but it's how much and how they are handled that is the real determining factor.
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