Who is Professor Fenton J. Fleabottom/Reginald Robertson Crockett from The Mostly True Adventures of Homer P. Figg and what is their importance?

Professor Fenton J. Fleabottom is a medicine man who runs a traveling show. Fleabottom travels around the country, putting on something like a freak show and selling his elixir, a medicine that Homer soon learns is only whiskey. Fleabottom is only an alias, however, as Homer later learns. Fleabottom is really Reginald Robertson Crockett, a Confederate loyalist who moves around the North collecting information that he then sends to the Confederate military. Fleabottom is caught when his brother, the messenger, is caught by the Union military. However, Fleabottom escapes, only to be killed on the battlefield at Gettysburg.