What was the use to tell Jim these warn’t real kings and dukes? It wouldn’t a done no good; and besides, it was just as I said; you couldn’t tell them from the real kind.
– Mark Twain
The Adventures of Huckleberry Finn, Chapter 23. Huck has figured out that swindlers and con artists the Duke and King are not the royalty they say they are. But he wants to protect Jim from this knowledge.