Mark Twain

Mark Twain was an author. At some point, the Doctor had edited Twain's first draft of Huckleberry Finn. Twain was apparently horrible at spelling, and the Doctor's editing was what made him able to submit the manuscript. As a reward, he gave the Doctor an original Paul E. Wirt pen. (PROSE: Shroud of Sorrow)

, also famously known as Mark Twain, once gave the Doctor a stetson hat, which the latter finally got around to wearing when he visited the Lakota Sioux Nation in his eighth life. (COMIC: Bad Blood)