Elementary, my dear Watson!

You read, you read and you read and you think you know something and then you get surprised. I have read and enjoyed both A.C. Doyle (Sherlock Holmes in particular) and P.G. Wodehouse all of my adult life. I knew that the stock phrase "Elementary, My Dear Watson!" was, like "Play it again, Sam", a line never present in the original text.

But I did not know that Wodehouse was the progenitor of that line. From Sherlock Holmes: examining the evidence – in charts:

"Elementary, my dear Watson!" was never said by Sherlock Holmes in any of the stories. The line was first used by PG Wodehouse in an affectionate parody.

The original reformulation is from Psmith, Journalist by P.G. Wodehouse.