"Nearly everyone knows that Judith" joke

Nearly everyone knows that Judith Martin, better known as Miss
Manners, the syndicated columnist, is exceedingly correct. Last
week, she saw an advertisement in the newspaper that a Maryland
jewelry store was having a sale in her silver pattern. Upon arriving
at the store, she told the jeweler she was looking for additional
dessert spoons in her pattern and had been making do with the larger
soup spoons.
"That's not much of a hardship," the employee said. "It is
for me," Martin responded. Caught up in the moment, the saleswoman
joked, "Who do you think you are, Miss Manners?" The easily
recognizable Miss Manners looked at the woman, unable to respond. And
then it registered. "Oh my God!" the saleswoman said.
from the Jan 26 San Jose Mercury News