What is a Lemon-entry?

Question

I don't get the Holmes Joke with the punch line "It's a lemon entry, Watson" What does it mean?

Answer 1

It's a pun. Sherlock Holmes is oft misquoted as saying 'Elementary my dear Watson'. (This quote never actually appeared in any of Conan Doyle's books, although Holmes once did say 'Elementary'. when Watson asked how he solved a particular case, but has become part of the Sherlock Holmes culture over the years.)

If you know the joke I think you refer to you should get it now although the punchline I know differs very slightly to say 'A lemon entry my dear Watson.'