Who is Ferguson/Billfinger from The Innocents Abroad and what is their importance?

A. Billfinger is a professional tour guide. Twain and his companions find his name so ridiculous that they rename him a good English name, Ferguson. Ferguson starts out very professional, but he soon turns money hungry and takes advantage of the newcomers to line his own pockets. Throughout the book, in many different countries, Twain mentions Ferguson as a source of shady tourist information. Later, the reader comes to realize that Billfinger is not the only Ferguson. But in fact, Ferguson is the pseudo-name of every guide the men ever hire during the trip.