Mark Twain is an American author and humorist who wrote during the 1800s. His most famous novels are Tom Sawyer and Huckleberry Finn. He also wrote other novels, including A Connecticut Yankee in King Arthur's Court, an early time travel story that includes Trans-Dimensional Hopping but does not end the way one might expect. Twain is the author of many short stories, autobiographical accounts, and essays. One such essay is Fenimore Cooper's Literary Offenses, in which Twain explains why bad writing and Mary Sues are a bad idea.
Twain may have been the first person to kill a Mary Sue (or, more correctly, a Marty Stu), in "The Story of the Good Little Boy." Twain uses a delightfully simple assassination strategy: He transplants the Marty Stu into a realistic situation. Rather than dying poetically as he expects (a tendency of Mary Sues everywhere), the Marty Stu suffers a great deal of embarrassment before being unceremoniously spread over several counties by an explosion.