In part II, chapter 4 of Foundation by Isaac Asimov, we meet the character of Lord Dorwin. Lord Dorwin has a speech impediment (later implied to be voluntary): he says "w" instead of "r" (much like Pontius Pilate in Life of Brian).
However, at least in my copy of the book, one of the first lines that we hear coming out of his mouth is
A gweat achievement, this Encyclopedia of yoahs, Hahdin. A feat, indeed, to rank with the most majestic accomplishments of all time.
He says "rank" instead of "wank" here. Why? At what level did Dorwin's speech impediment disappear for that one word? Is it Dorwin who doesn't want to say it? Is it the narrator? The author? The publisher? Or just a typo? Is there any way to know?