"Mistaken Identity" is an amusing anecdote recounted by the famous author Mark Twain about an experience he once had while traveling by train to New York. When he and his companion change trains, Twain asks the young man in the booking office if he can have a sleeping berth. The clerk rudely informs Twain that no such berths are available. So Twain asks another official if he can find him some modest little corner somewhere in a sleeping car. But the official brusquely tells him that every available space is full and to stop bothering him.
However, things suddenly change when it becomes clear that the porter and the conductor recognize Twain—or so he thinks. They immediately start acting all helpful and obliging; nothing's too much trouble for them. The conductor finds Twain and his companion a big family compartment complete with two berths and a couple of armchairs. Twain is convinced that they're only receiving this special treatment because the porter and the conductor realize there's a famous writer on board.
But Twain's ego receives a bit of a knock when the porter wrongly identifies him as McClellan, that is George B. McClellan Jr., former mayor of New York. This is somewhat ironic as Mark Twain wasn't of course his real name, but Samuel Langhorne Clemens. Twain was also once mistaken for Melville Fuller, Chief Justice of the US Supreme Court, whom he greatly resembled. When asked for Fuller's autograph one day, Twain obliged with a characteristically witty response:
It is delicious to be full, but it is heavenly to be Fuller. I am cordially yours, Melville W. Fuller.