The World’s oldest known creature, a mollusc, was 507 years old until scientists killed it by mistake.
Rio de Janeiro means “January River” and it was called that by mistake. A Portuguese explorer thought the bay was the mouth of a river.
David Bowie declared himself gay in 1972 then bisexual in 1976, but ultimately admitted that those declarations were a mistake.
In 2013, Bill Gates admitted that the Ctrl+Alt+Delete command was a mistake, and should have been a single button.