How 9/11 Changed What Americans Laugh At
A now-familiar joke that started circulating within the first year or two after September 11, 2001, goes like this:
“Knock-knock!”
“Who’s there?
“9/11.”
“9/11 who?”
“You promised you’d never forget.”
The punch line, of course, refers to the refrain that became ubiquitous in the United States following the attacks that killed nearly 3,000 people and shattered the country.