1. Sherlock has been on film for over a century.
The cinema juggernaut started to roll with the short silent film, Sherlock Holmes Baffled, dating from around 1900.
2. You could have known the sleuth by a different name.
3. And John Watson might have been Ormand Stacker.
4. A Study in Scarlet was originally A Tangled Skein.
5. Mycroft only appears in two Holmes stories.
Although one of the most compelling figures in the Holmes stories, he actually appears in only two - 'The Greek Interpreter' and 'The Bruce-Partington Plans' - and is referred to in just two others.
6. Arthur Conan Doyle's old teacher inspired Sherlock Holmes.
Published in 1892 [The Adventures of Sherlock Holmes] was the first collection of the detective's cases that had originally appeared in Strand Magazine and was dedicated to Doyle's 'old teacher' Joseph Bell, considered the inspiration or model for Holmes.
7. Sherlock began with a sentence fragment.
8. Holmes didn't wear a deerstalker cap.
The majority of fans would immediately identify him by his cap and cape, but in the stories he only wore them for cases that took him to the country. Watson, however, never specifically identified the headgear as a deerstalker.
9. Watson's wife has some explaining to do.
Everyone knows that Dr Watson is called John. So why, in 'The Man with the Twisted Lip', does his wife call him James?
10. A method actor took his portrayal of Holmes too seriously.
11. Holmes' famous tagline is a fake.
Holmes never says 'Elementary, my dear Watson.' The closest he gets is in 'The Crooked Man' when after Watson cries ... 'Excellent!' Sherlock dryly replies, 'Elementary.'
12. Queen Victoria had a soft spot for Sherlock.
Holmes solved hundreds of cases, including one ('The Bruce-Partington Plans') that earned him a private audience at Windsor with Queen Victoria from which he returned with a handsome emerald tiepin.
13. Fandom crossover is real.
14. Mrs Hudson might be more than she lets on.
There has long been speculation that Mrs Hudson is Holmes' agent in the household of the German spy in 'His Last Bow', but quite why the author would use her in a story set in 1914 and fail to have either Holmes or Watson refer to her at any time as 'Mrs Hudson' as they have been doing since 1889 seems a mystery.'
15. Moriarty and Sherlock might have had a history.
Much speculation has been devoted in books and films to the possible genesis of the Holmes-Moriarty struggle.
Theory: Moriarty was a young Sherlock's maths tutor.
Source: Sherlock Holmes of Baker Street (W.S. Baring-Gould)
Theory: Moriarty had an affair with Sherlock's mother
Source: The Seven-Per-Cent Solution (Nicholas Meyer)
16. A Study in Scarlet was a family affair.
17. Doyle wanted to kill Holmes off out of boredom.
[W]ithin two years he had grown so tired of Holmes that he decided the time had come to kill him off, complaining that it 'takes my mind from other things'.
18. Sherlock Holmes and Dorian Gray might as well be brothers.
19. There is no 221B Baker Street.
In Holmes' time, Baker Street was short, barely over a quarter of a mile, and house numbers only got up to No. 85. In 1930, however, the entire length of the thoroughfare was renamed Baker Street, requiring a renumbering. A Georgian hous, No. 41 Upper Baker Street, was redesignated 221 Baker Street but was demolished the same year.
These facts are based on excepts from The Elementary Sherlock Holmes: Things You Didn't Know About Literature's Greatest Detective, published by Portico, and the current Sherlock Holmes exhibit at the Museum of London, 'Sherlock Holmes: The Man Who Never Lived and Will Never Die'.