"Mary Sue"

A "Mary Sue" (a phrase based on a Star Trek fan fiction story poking fun at all the overdone fan fictions) refers to a character who stretches the bounds of believability. A Mary Sue is more powerful than he/she should be, is probably the son of a god or a king, and takes up too much of the story.

A Mary Sue is also nauseatingly cliche, and is generally the best at everything. There are Mary Sue story devices, where a highly unlikely and suspiciously lucky thing happens that takes care of everything.

Like, in Harry Potter and the Chamber of Secrets. Harry, Ron, and Lockhart are down in the sewers. Harry standing at the Basilisk that can kill him with its eyes. Fawkes the Mary Sue phoenix eats his eyes out. Harry is hurt. Fawkes the Mary Sue has healing tears! Harry and friends are stuck in the sewer. Fawkes can carry many times his weight, and flies them out! Yay for Fawkes, right?

Wrong.

Though somehow Harry Potter got away with it (it helped that all it's abilities where mentioned beforehand, so it makes sense to the audience), you probably won't, or rather, shouldn't. Mary Sues hurt the story, and I don't want to catch you using them.

I'll be watching.