The 'Other Darrin' trope is when an actor is suddenly replaced, is named after a character in which sitcom?

The 'Other Darrin' trope is when a new actor is brought on to play the same character as a previous actor who has left the series, with no explanation for the switch given to the audience. Named for the famous Darrin swap case: Dick York to Dick Sargent, on "Bewitched".

Sargent-York became a notable phenomenon only with the rise of series television. Prior to TV, there was no expectation that a role in a theater production would be played by the same actor. It was, and still is, assumed that any production of a particular work would seek out whatever actors it wanted for the roles, and a single production can feature different actors in the same role on successive nights.