Adaptation Overdosed: Holmes might very well take the ultimate crown here. The Other Wiki says he is the most frequently-portrayed character in the history of cinema, having been played (by some counts) by over 75 different actors in 211 films. In a book on the subject, Holmes scholar Ronald B. DeWaal lists an astonishing 25,000 Holmes-related productions and products. Or just look at the Franchise page for our list.
In the original novels, Holmes never actually uttered the exact phrase "Elementary, my dear Watson". He uses the phrase 'elementary' on occasion, and often refers to Watson as 'my dear Watson' but never combines the two. The phrase actually comes from a P. G. Wodehouse novel.
Nor did he ever cry, "Quick, Watson, the needle!" That phrase originates in Victor Herbert's comic operetta The Red Mill, where it's used by a character who's impersonating Holmes.
Likewise, the deerstalker cap and Inverness coat are never mentioned in the stories proper, and while Sidney Paget did at times draw him wearing one or the othernote a deerstalker in "Silver Blaze", an Inverness coat in "The Blue Carbuncle", he never put them both together. Nor would Holmes, despite his recurrent flakiness, have worn such a countrified outfit in the middle of London.
Lampshaded in the recent Sherlock Holmes Versus Jack the Ripper game, in which at one point Sherlock asks Watson to "bring [him] that old deerstalker [he] never wear[s], but everyone seems convinced [he] wear[s] all the time".
And played with in the second season of Sherlock BBC, where Sherlock pulls on a deerstalker cap in an attempt to avoid paparazzi, and merely ends up with the press considering him the "man with the funny little hat" with pictures to back it up.
Parodies of Sherlock Holmes stories often begin with "The Case Of...", but the titles of (most of) the original stories begin with "The Adventure Of..." instead. Only one story title ("A Case of Identity") even uses the word "case".
Internet Counterattack: Holy damn, the reactions to Holmes's death in "The Final Problem." The Strand's subscription rate dropping tremendously, thousands and thousands of hate mail for Doyle, Doyle getting attacked in the street numerous times, young women wearing black, men wearing black armbands, Prince Bertie expressing outrage, Conan Doyle's mother complaning and there were even rumors of Queen Victoria herself among the people who disliked Doyle's decision.
Magnum Opus Dissonance: Conan Doyle respected Holmes enough to avert dropping a bridge on him in "The Final Problem", feeling the character deserved to go out with a bang. He did, however, resent that the character was so large that nothing he, Doyle, ever wrote would ever be able to crawl out from under Holmes's shadow.
Money, Dear Boy: One of the reasons Doyle eventually brought Holmes back was because of the enormous sums of money editors were offering him.
In "The Adventure of the Blue Carbuncle", Sherlock determines that a man is intelligent by his hat size, reasoning that a man with a big head has a large brain, and therefore is smarter than average. While there is some dispute among modern scientists as to whether there's any correlation brain size and intelligence, any correlation would be subtler and less pronounced than the one Holmes claims.
Brain Fever, which is not real, appears in several stories.
In several stories Holmes attributes things like personality and interests to genetics.
The science in "The Creeping Man" is flawed, to say the least, unless you consider the effects of the "potion" to be psychosomatic, and Professor Presbury a highly suggestible lunatic. The idea of using serums taken from animals for rejuvenation and invigoration was taken quite seriously by many scientists in the late 19th and early 20th centuries.
The biology in "The Speckled Band" is also flawed. Snakes do not work that way.
Word of Dante: Holmesian fanon (known amongst fans as The Game, since long before the existance of the internet) is varied and has many varied sources from many mediums. The three main sources, however, are William Stuart Baring-Gould's The annotated Sherlock Holmes and Sherlock Holmes of Baker Street, and Leslie Klinger's The New Annotated Sherlock Holmes.
Similarly, Mycroft Holmes and the Diogenes Club have been expanded by later pastiches (notably The Private Life of Sherlock Holmes) into the Head of the Secret Service and one of its fronts respectively, when in the original canon they're little more than what Doyle presents them as (a Brilliant, but Lazy civil servant and a club for reclusive eccentrics).
The 2009 film
Credits Gag: There are a couple, mostly in the juxtaposition of assorted credits with images from the film. The best of these is that the Costume Designer's credit appears with an image of the naked Holmes tied to a bed.
Deleted Scene: So, Irene never got around to trying to stab Holmes with a hair pin or kneeing him in the... meerschaum, eh?
Dyeing for Your Art: Downey did this movie in between the first two Iron Man movies. Look at how beefy Tony Stark is compared to how wire-thin Holmes is. That takes dedication.
Rob also was meticulous in making sure his accent was perfect for the character and historical period. As per Guy Ritchie's interview on Top Gear, he succeeded.
It was perfect for modern perceptions, but it wasn't historically accurate. Historical British sounded much closer to modern Americans than modern Britons. It mainly revolves around rhotic speech.
Holmes himself is played by Robert Downey Jr., making him a Fake Brit.
Canadian actress Rachel McAdams plays the American Irene Adler.
Dredger, the large French man from the first movie, is actually French-Canadian.
William Hope, a Canadian actor, played Standish, the American ambassador in the first film.
Noomi Rapace, a Swedish actress, plays Simza, a French gypsy, though Rapace might have some Roma ancestry.
Fan Nickname: Watson, due to being taller, thinner, younger and more Jude Law than some previous portrayals, quickly became known as Hotson.
Stephen Fry's version of Mycroft Holmes quickly took on the nickname "Frycroft".
Fandom Nod: In the extended preview (aired during the Monk series finale), there's yet another clip of the Holmes-Watson Vitriolic Best Buds routine, then a cut to Adler going "They've been flirting like this for hours." To the general public, a funny joke. To those aware of the Holmes/Watson-shipping fanbase, bloody hilarious. As it happened, this seems to have been a deleted scene referring to Watson's bickering with a boat captain.
The Other Darrin: Moriarty played by Jared Harris, in a way. He appears in shadow in the first movie and is played by Ed Tolputt in an uncredited role.
Hey, It's That Guy!: Both Peter Cushing and Christopher Lee have portrayed the great detective with great acclaim in two separate occasions. Peter Cushing in particular has been considered amongst the best out of the more than 75 actors to have portrayed the character, which include the likes of Jeremy Brett, Basil Rathbone and Vasily Livanov, and was known to have an encyclopedic amount of Holmesian knowledge.
While Edward Hardwicke was bald and wore a wig for the role of Watson.
Plus, Jeremy lost several pounds to acquire Holmes's slender look.
The Other Darrin: Between the first and second series, Edward Hardwicke replaces David Burke as Watson. (Burke actually suggested Hardwicke to the producers.) The distinction is quite sharp - The Final Problem uses Burke, but Holmes returns to Hardwicke in The Empty House (they even reshot a few scenes with Hardwicke for flashback purposes). Overall, David Burke came across as much younger, more naive Watson, albeit one who resembled the original illustrations. Edward Hardwicke, however, was older, more distinguished, and more ex-military. Most fans agree Hardwicke was the more memorable Watson.
Real-Life Relative: After a fashion. In the adaptation of The Problem of Thor Bridge, the role of Neil Gibson is played by Daniel Massey, whose sister actress Anna Massey had been married to Holmes actor Jeremy Brett from 1958 to 1962. Although the couple had divorced, due to Brett's bisexuality, the split had been amicable, and the two had remained friends.