The New York Times has corrected an article that mistakenly referred to the Great Depression of the 1930s as "the time of shedding and cold rocks".
One of its editors had installed software that adds references to snakes to websites.
The substitution was missed and published online, but did not appear in the print edition of the newspaper.
The newspaper blamed an "editing error involving a satirical text-swapping web browser extension".
The Millennials to Snake People add-on for Google's Chrome browser was created by coder Eric Bailey, who had noticed a surge in news stories blaming so-called millennials for the world's problems.
He decided changing the term "millennials" to "snake people" in news articles and on websites, and making other snake references, would be funny.
The New York Times correction offered readers a "pro tip" to avoid mistakes, advising: "Disable your Millennials to Snake People extension when copying and pasting."
The mistake appeared in an article fact-checking President Donald Trump's claims on trade deficits.
In 2016, Wired magazine made a similar mistake and published an article in which Donald Trump's name was replaced with "someone with tiny hands".
The error made it past the magazine's production team, who had assumed it was an intentional joke.