With more and more movies turning to existing properties instead of original scripts, actors being asked to embody established characters is now commonplace, not a rarity. The latest novel-to-big-screen adaptation puts Tom Cruise in the extremely-oversized shoes of Jack Reacher, and while it may be the latest instance of an actor cast in a role bearing almost no resemblance to themselves, it's certainly not the first.

Comic books, novels, TV shows and the inevitable reboots to come all mean that more and more famous faces and newcomers will be asked not to make people care about new characters, but live up to the expectation and legend of ones they already cherish.

The list is only going to get longer as the years go by, here's our Top 10 Characters That Look Nothing Like Their Source Material. Some might surprise you.

Tom Cruise Jack Reacher

We start of course with Tom Cruise, occupying the title role in the upcoming Jack Reacher. The recurring star of Lee Child novels, Reacher is a remorseless, unstoppable force of a man, with his military service spent as part of an elite investigative unit called upon when the Army's most highly-trained operatives were up to no good. Cruise has played roles along the same lines, and proved he could be as intimidating and deadly in the first teaser trailer.

Yet anyone who has read a Child novel knows that Cruise is, literally, about as unlike Reacher as is feasibly possible. Described in the books as 6'5", 250 lbs, and sporting blond hair and blue eyes, Cruise's small frame and dark coloring aren't quite a match.

Cruise's casting as Reacher may take the cake, but for now, it seems like the decision could end up being a wise one. Child has long maintained that his character's size was merely a symbol of his determination and unyielding drive, which Cruise is achieving through non-physical means.

Ben Affleck Jack Ryan Sum of All Fears

Adaptations of novelist Tom Clancy's perennial hero have regularly strayed for the sake of Hollywood convention, but for The Sum of All Fears, Paramount took things to a new level. Those who saw the movie know that Ben Affleck was cast as Jack Ryan for the then-planned-reboot; a promising young CIA analyst, though not yet a field agent.

The same basic plot worked for Alec Baldwin's Ryan in The Hunt for Red October (1990), so it's not hard to see why they chose to follow the same route. The only problem is that in Tom Clancy's continuity, Ryan wasn't just 40 years old and married when the movie occurs, he'd been appointed Deputy Director of the Central Intelligence Agency. His career had him just four years away from being President of the United States, no less.

Luckily, the source material seems to be adhered to in the upcoming Jack Ryan reboot, with Chris Pine now occupying the role. Maybe it will even be set in Jack Ryan's early adulthood, when he was just a millionaire investment banker-turned-professor of history at the US Naval Academy. Wait...what...?

Will Smith Wild Wild West Robert Conrad

In 1965, the genre of western films and TV shows was swiftly making way for the intrigue and tension of spy thrillers. The shift led to the creation of The Wild Wild West on CBS - essentially, a spy story following two Secret Service agents in the 1870s. Modern audiences may not know Robert Conrad as the face of James T. West, as close as one could get to James Bond with a six-shooter. But they sure know the remake.

The Fresh Prince himself, Will Smith was cast as the new Jim West in an updated version of the agents' efforts to protect President Ulysses S. Grant from all manner of villains. While Conrad was as much a heartthrob as Smith in his day (black and white six-packs will never not be weird) but that's where the similarities end.

We need only remember that the theme song for the remake featured Sisqo, and are instantly glad the film never received a sequel. Smith and director Barry Sonnenfeld may have sullied the series' good name, but to Conrad's credit, he had a sense of humor. When Wild Wild West (1999) was awarded five Razzies, Conrad was there to accept them in person. Smith has since apologized to Conrad directly.

James Bond Hoagy Carmichael

Sean Connery may have become the face of James Bond, but the secret agent fans know  isn't exactly what creator Ian Fleming had in mind when writing. Fleming's Bond was physically described in his first novel, Casino Royale, as a mix between himself and American singer Hoagy Carmichael (pictured left). What audiences got was a ruggedly handsome and well-fed Connery - not that we're complaining.

The decision to go in a more 'suave' direction for film made sense, but the comparisons to Carmichael persisted in the novels, with various women noting the resemblance but distinguishing something far from alluring about Agent 007. Specifically, "something cold and ruthless" according to Vesper Lynd, and Gala Brand's claim in Moonraker that Bond looked "cruel in the mouth, and the eyes were cold."

Fleming's Bond never had issues with women, even with his sharp bone structure, but the source material does directly contradict those who doubted Daniel Craig as a suitable choice when cast for Casino Royale (2006). Craig may not exude the same debonair...air as Connery, but his harsh features and at-times callous expression make him physically closer to Bond than any other.

Kane and Lynch Bruce Willis Jamie Foxx

Video game fans may already know the big screen translation of Kane & Lynch: Dead Men (2007) and its...unexpected casting. The story follows two escaped death row inmates: Adam 'Kane' Marcus, a no-nonsense, grizzled mercenary complete with scarred-milk-eye, and James Lynch, a gunman with a sense of humor - who also happens to be schizophrenic.

When Bruce Willis was first confirmed to star in the film, many hoped the aging action star would welcome a change, and be the one sporting the shoulder-length hair and mental affliction. Perhaps that was hoping for too much. Oh well. So who would be playing the aging, balding, unkempt, overweight and mentally deranged Lynch to Willis' Kane?

Oh that's right, Jamie Foxx. The casting was the first sign that the game's title and loose (and honestly, formulaic) plot might be the only thing the producers were after, supported by a leaked script that removed Lynch's mental condition and crude demeanor entirely. Since then the production has been swamped, meaning fans might not get to enjoy this completely modified adaptation at all.

Keanu Reeves John Constantine Hellblazer

It's a tough question: how do you make magic in the modern world work? Our answer: pick up an issue of Hellblazer. The occult detective John Constantine may have been solely created to resemble singer/musician Sting, but since inception has become Vertigo's most iconic and unique antihero.

The epitome of sarcasm, crude language, and British punk counterculture, who better to play him in the movie than Keanu Reeves? Trading his blond hair for black, grizzled exterior for baby-face good looks, Liverpool accent for American, and even his uniform of a tan trench coat for black, the magic detective of Constantine bears zero resemblance to the original (although a second attempt may be on its way).

The inexplicable changes extended to secondary characters as well, like Constantine's longest and best friend Chas Chandler, portrayed on film as a fast-talking apprentice in Shia LeBouf. Why, we can't possibly answer, since at this point in the comic books, Chas is a grandfather.

...In hindsight, that might've been a stretch for LeBouf.

Catch Me If You Can Frank Abagnale

One of the too-good-to-be-true biopics, Catch Me If You Can followed the dramatized events of prolific con-man and impersonator Frank William Abagnale, Jr. Having masqueraded as an airline pilot, doctor, lawyer and more, Abagnale's life was one destined for the big screen.

Leonardo DiCaprio embodied the confidence man with a performance that helped cement his career as more than just a youthful face; and that's the problem. Abagnale consistently maintained (and the photos support it) that it was his ability to look much older than his actual age that allowed him to fly over 1,000,000 miles posing as a PanAm pilot - by the time he turned 18.

Casting DiCaprio, an actor whose unchanging youthful appearance hindered his casting as more than a heartthrob, was an odd choice to say the least. We'd wager he'd have trouble buying a beer before he turned 25, let alone playing a convincing pilot before he was able to drive. Biopics generally receive a dose of glamour in their shift to the big screen, but the truth is: if Frank Abagnale Jr. looked anything like Leonardo DiCaprio, there wouldn't be a story to tell.

Batman Movie Michael Keaton

He's one of the most famous comic book characters, and the embodiment of terror; the one man able to strike fear in even the most hardened criminal. So when director Tim Burton got the chance to cast an actor in the role of Batman (who wouldn't merely be parody or camp), who better than Mr. Mom?

Michael Keaton was on virtually nobody's list of dream casting for Batman, and fans made their outrage heard. It isn't hard to see why a 5'9" actor known for comedic roles over dramatic ones raised eyebrows, since it's still hard to picture what a serious, depressed Michael Keaton actually looks like. Luckily for all involved, the choice paid off.

Comic book and movie fans will debate the best incarnation of Batman until the end of time, but there's no denying the chemistry between Jack Nicholson's Joker and Keaton's Batman as some of the best in the comic book movie world. We wouldn't have bet money that Beetlejuice could give the world anything but a horribly misguided version of Bruce Wayne, but Keaton and Burton made it one to remember.

John Wayne The Conqueror Genghis Khan

John Wayne. The Duke. The quintessential cowboy, and...Mongolia' greatest ruler? We've steered clear of movie adaptations that change the race of existing characters, since more than skin color goes into bringing a role to life. But we have to make an exception for John Wayne's turn as Temujin/Genghis Khan in The Conqueror for its place in industry history and the talent attached.

Casting an actor more well-known for his cowboy persona as Genghis Khan is so absurd, so nonsensical that it's hard to credit the filmmakers with racism as opposed to simple lunacy. Produced by magnate Howard Hughes, who purchased every print of the film in an effort to put the movie behind him, The Conqueror is reportedly one of the films that Hughes watched obsessively during his infamous seclusion.

Possibly the cause of 91 cases of cancer among cast and crew (the movie was filmed downwind of a US nuclear weapons testing site), The Conqueror's casting has to stand as one of the worst decisions ever made in film. Wayne himself reiterated the lesson it taught: "not to make an ass of yourself trying to play parts you're not suited for." We'd have to agree.

Avatar Last Air Bender Casting Choices

Horrible casting, atrocious direction, script and pacing issues aside, it was the massive changes to the central characters of M. Night Shyamalan's The Last Airbender that doomed the film to its fate. For those who never saw the TV show it was based on (shame on you!), and simply called it quits after the movie, we can't make this any clearer: none of the characters were faithfully translated.

Sokka, the bumbling, ungifted goofball who takes himself seriously (but garners only laughs) became a tough-as-nails, no-nonsense protector to his sister, Katara - the one who really led with her heart, not militaristic courage. But no adaptation is worse than the titular Airbender, Aang. The embodiment of childish wonderment and playfulness, the film portrays a brooding, angry, and all-too-prepared savior. Even the pronunciation of his name was inexplicably changed by Shyamalan...it should have been a sign.

Changes of this magnitude aren't exactly rare, but fans of the TV show unfortunate enough to witness the film will agree: a majority of The Last Airbender's cast of characters share almost nothing besides name and haircut to the source material. That the changes all worked to form a downright terrible film just make it worse.

That's just 10 of the most egregious adaptations in our opinion, but the sheer amount of novels, comic books, video games and stage plays mean there are plenty more. We welcome all contributions:

What casting decision or 're-imaginings' irked you the most when first seeing them? Were there any that cost the film any chance of success, or perhaps defied expectations and captured the heart of the character despite differences?

Hopefully Tom Cruise can pull off that challenge this Friday with Jack Reacher, for both audiences and fans of Lee Child's hulking hero.

Follow me on Twitter @andrew_dyce.