Answer: Movie

The original canon of Sherlock Holmes literature, the direct works created by Sir Arthur Conan Doyle himself, are comprised of 56 short stories, four novels, and a number of vignettes, play adaptations, and essays involving Holmes. At no point, in any of the works directly penned by Doyle, does Sherlock Holmes ever utter the iconic and often repeated phrase, “Elementary, my dear Watson.”, to set up an exposition wherein he explains how he has masterfully deduced the nature of the puzzle before him.

Holmes does, however, say those exact words in the 1929 film The Return of Sherlock Holmes, and again in the 1939 film The Adventures of Sherlock Holmes. The latter film enjoyed a significantly wider reception and is credited with popularizing the phrase. So popularizing, in fact, that it entered deeply enough into the public consciousness such that generations of people have erroneously assumed the line was from the original literature penned by Sir Arthur Conan Doyle.

Over six decades later, the quote would be enshrined by the American Film Institute, where it ranked the phrase 65th in its compilation of 100 memorable movie quotes in 100 years of American cinema.