Victor Hugo's novel Les Misérables may not actually hold the record for most adaptations, but the list is still very impressive. There are currently 66 adaptations (although that's sometimes stretching the word a bit). A handful of these are easily available; die-hard fans have managed to see more than twenty. Check Wikipedia for a list. Adaptations are in this article mainly referred to by production year.
Versions of Les Misérables with their own trope pages include:
Other adaptations provide (in addition to those shared with the novel) examples of:
Adaptational Heroism: Arguably, Éponine. Her cruelty towards Cosette when she is exploited into being her family's slave tends to be downplayed in film adaptions (and omitted entirely in the 2012 film), and it is implied she actually wanted Marius to die at the barricades in the book.
Adaptation Dye-Job: In the book, Fantine and Enjolras are blond, Marius has curly black hair, and Cosette is brown-haired. Especially the last one is often ignored. Seems The Ingenue just has to be blonde.
Adaptation Explanation Extrication: Too many to count, but a good one is that both Javert's suspicion that Madeleine might be Valjean and the reasons for Champmathieu being mistaken for Valjean, while lengthily explained in the novel, are often condensed to "He looks like Valjean".
In a plot stretched over nearly twenty years, probably the most frequent one is characters failing to get older:
Gavroche in the 2000 miniseries starts off older than Cosette, but is still the same age nine years later.
Cosette in both '52 and the '82/'85 adaptation. Although in one, she stays the same age from when Valjean fetches her to adulthood and in the other from when Fantine leaves her to when Valjean fetches her.
Adaptational Attractiveness: Usually with Javert, but some movies have Fantine look incredibly pretty (and above all healthy), when she's supposed to be dying of TB. Sometimes Valjean — the 1978 version (starring Richard Jordan as Valjean) was released on video a blurb beginning: "Jean Valjean, a handsome young woodcutter..."
Adaptational Badass: Stretching it a bit, but Cosette is basically this in the 1992 French cartoon.
Adaptational Villainy: Javert in the novel may be Valjean's antagonist for most of the time, but some adaptations portray him as outright evil, sometimes even brutal ('35, '52, '98...). This is often due to the removal of the Thénardier couple, who would otherwise serve as primary antagonists.
Animated Adaptation: Several, including at least four anime adaptations. The three Soviet cartoons that focus on the children are also worth a mention; two are called "Gavroche" and are only propaganda.
Averted with the 1964 Italian miniseries, which is eleven hours long and has managed to put in most of Hugo's long narrative passages, such as some information on the underworld or the battle of Waterloo.
Deadpan Snarker: Javert is allowed to keep a few lines in some adaptations: 1933, 1963, 1972 and 2000 most prominently.
Death by Adaptation: Rare, since nearly everyone dies anyway, but the '47 adaptation in addition kills off notorious Karma HoudiniThénardier by letting him fall through a skylight.
Downer Ending: Especially in the 1985 movie, where Cosette and Marius only arrive after Valjean has died alone and unloved.
Dudley Do-Right Stops to Help: Jean Valjean repeatedly detours from his flight from Javert in order to help those in need, which on multiple occasions nearly gets him captured by the inspector.
The Film of the Series: There's a French 26-episode cartoon from 1992. In 1993, a 90 minute movie version was released.
Galley Slave: There is some confusion going on here anyway, as the novel frequently refers to Valjean as a galley slave. This is due to the words "galley" and "galley slaves" continuing to be used in French for a kind of penitentiary (bagne in French) and their inmates, long after they were not actual slave galleys anymore. Two movies (from '35 and '52), however, are (in)famous for taking the word too literally.
The Game of the Book: Actually called "Les misérables: The game of the book", it's a point-and-click adventure with very simple graphics in which you basically have to make the story happen.
Arm Joe, a StreetFighter esque fighting game that utilizes the characters from Les Mis.
Happily Ever Before: Some movies commit the sin of ending with Javert's suicide, leaving Valjean to live happily ever after.
Heel-Face Turn: Valjean gets the biggest one after being pardoned by the bishop. Javert gets one when Valjean refuses to kill him. Fantine gets one in some versions; Marius can have up to four. The more complete the movie, the more heel face turns included.
Hellhole Prison: One thing nearly all adaptations appear to agree on, although some emphasise it more (1935, 1952, 1978, 1982...) than others (1958, 1972, 2000...).
Historically correct (yellow trousers, white shirt, red vest, and jacket and green caps for lifers or red caps for non-lifers): 1925, 1933, 1958, 1992, 2000
Partially correct: 1978
Just any kind of prison uniform: 1947, 1955, 1964, 1972
Hollywood Old: Valjean is supposed to be over sixty at the end? Incredible in the cases of Fredric March, Michael Rennie, Richard Jordan, and downright ridiculous with Hugh Jackman!
Kill 'em All: One of Victor Hugo's favourite tropes. Some adaptations don't seem to like it, though. The record is kept by the 1992 French cartoon with exactly one named character that dies.
Lawful Stupid: Javert has tendencies towards this in the book, but in some adaptations (notable the ones from '35 and '52) he as good as flat out refuses to take any responsibility for his actions, blaming each and every decision on the law.
The 1992 French cartoon. This is the adaptation where no death occurs on screen. Cosette also has a dog friend, Amiral.
There are several Indian adaptations ('50, '55, '72) that have this. Bollywood!Les Mis probably says it all.
Line-of-Sight Name: How Jean Valjean chooses the alias of M. Madeleine in the 1952 movie, somewhat undercutting the symbolic significance of the name.
Lost in Imitation: Not too many, since there are so many different adaptations, but a few notable ones are:
Who still remembers that Javert did not devote his entire career to tracking down Valjean?
Les Misérables is not only a musical: Liam Neeson's most famous quote concerning the '98 adaptation: "One of the greatest novels in Western literature, and all everybody's asking is, 'Do you sing in it?'"
Meaningful Echo: The 1935 version has one. When the Bishop gives Valjean the candlesticks, he tells him, "Life is to give, not to take." Later, Valjean passes on the candlesticks to Cosette and Marius, and tells them, "Remember, as was once told me: life is to give, not to take."
Nightmare Sequence: Valjean's night at the bishop's house is this in a few adaptations, usually in the form of a traumatic flashback dream (examples in the movies from 1935, 1989, 1998...).
No Name Given: Usually, as in the novel, Inspector Javert, Fantine, both Thénardiers, all of the students except Marius Pontmercy (and Jean Prouvaire, if he appears). Most movies add Bishop Myriel and his sister and house keeper to that list. And Gavroche, though in the novel he's a Thénardier.
Dominique Zardi, in France known as the "king of supporting roles", starred in three adaptations: as Claquesous, Chenildieu and Cochepaille.
Lucien Nat plays Montparnasse in the '33 movie and M. Gillenormand in the '72 miniseries.
Henry Krauss played Valjean in the 1913 movie and came back in '33 as Myriel.
Émile Genevois, 1933's Gavroche, was a bus driver in the '58 version.
Georges Geret took over for Marcel Bozzufi as Javert for the third part of the '61-'63 adaptation. In 1972 he was back: as Valjean.
Chittor V. Nagaiah played "Valjean" in two Indian adaptations, from '50 and '72, respectively.
Sessue Hayakawa also played Valjean twice, namely in '50 and '64.
Joke or mistake example: Gino Cervi played Valjean in the Italian movie of 1947. Several webpages (imdb, most notably) credit him for an unnamed part in the '64 series, but so far it seems no-one has spotted him.
Rock Opera: The original French concept album was a complete show in and of itself, and is self-contained in the music.
Setting Update: The story was adapted to different countries and different eras several times, most notably to Japan (14 adaptations, although some of them are set in France), India (four times), and Egypt (twice). One French adaptation puts the plot into early 20th century France.
Shipped in Shackles: The 1978 movie in a rare example of historical accuracy in that movie, shows a group of convicts, of which Valjean is a part, being chained together by their necks before being transported to Toulon on carts. The scene where Cosette and Valjean watch such a chain gang pass by is included in the 1933 and the 2000 movie.
Spared by the Adaptation: Gavroche, Mme Thénardier, Valjean, Javert, Éponine, and all of the friends of the ABC manage to survive in at least one adaptation each. Although sometimes these are the adaptations aimed at kids.
Stern Chase: Javert hounding Valjean for decades. (Which is really an artifact of adaptation distillation/compression; Javert is not such a monomaniac in the book.) Some do at least give the impression he actually did other things, but keeps hearing about that ONE guy...
A Taste of the Lash: Well, the main character is an (ex-)convict, and some adaptations seem to be only too glad to make clear just how bad 19th-century French prisons were. Three movies show Valjean being flogged (1935, 1947, 1950) with three more heavily inferring it (1952, Egyptian 1978, and 2012).
Where The Hell Is Springfield?: Yes, original editions censored the town names Digne and Montreuil-sur-Mer. It's still easy to find out which city is meant, especially in the case of Montreuil (a road map description), and there is no need for cities like Morvein (1952 movie, no city of such name exists in France), Monteis-sur-Monteis (1978 movie; leaving aside the fact that it sounds ridiculous, “Monteis” doesn't actually mean anything in French) or Vigo (1998 movie, small town in northern Spain).
Wife Husbandry: In the 2000 TV miniseries, Valjean admits to Marius that he is in love with Cosette. Squick.
You Are Number Six: Valjean's prison number is mentioned by most adaptations, but few of them do more than name it. Many filmmakers seem to have a problem with the numbers that Hugo chose (24601 and later 9430), as the number often gets changed to: 2906 (1935 adaptation), 872 (1947 Italian adaptation), 1082 (1952 adaptation), 335 (1955 Indian adaptation), 1205 (1982 adaptation)...