Actors like Christian Bale and Daniel Day-Lewis have wowed audiences and earned plenty of awards for their ability to completely immerse themselves into roles and deliver stunning performances.
Many actors have 'gone method' in a bid to make their performances as authentic as possible, including putting on and losing weight, learning a new language or locking themselves in a hotel room for a month.
But sometimes it doesn't always end with adoration and awards, sometimes nobody cares about the effort put in, like...
10. Matt Damon endangers his health to star in a decent film, it goes virtually unnoticed
Everyone marvels about the weight loss of Christian Bale, Natalie Portman and Matthew McConaughey for their great film appearances, but one went completely unnoticed by most.
That was Matt Damon in 1996's Courage Under Fire - the actor lost 40 pounds (nearly three stone) to play a drug-addicted Gulf War soldier in the action film that it made him really ill.
The actor ran 13 miles a day on a very sparse diet, which made him so frail that he was put on medical supervision for several months after the shoot.
Despite all of the film's great reviews, Damon's extreme weight loss went completely unmentioned, which the actor said left him 'devastated' him after the film.
Still, while none of the reviews paid attention to Damon's efforts, Francis Ford Coppola was impressed and offered the lead role in The Rainmaker and Stephen Spielberg cast the recovered Damon in Saving Private Ryan.
9. Eric Stoltz got super into being Marty McFly, gets fired shortly after
One of the most famous 'almost castings' in film history is that of Eric Stoltz, the star of Mask (the one with the weird-headed kid, not the Jim Carrey one) filmed scenes for the time-travelling comedy, but then was replaced by Michael J. Fox early in production.
While filming his small amount of scenes, Stoltz insisted that everyone call him 'Marty,' even after the cameras had stopped rolling
Also, in the cafe scene with Biff where Marty pushes the towering bully, Stoltz insisted on putting all his force into the shove which left actor Thomas F. Wilson with bruises.
Producers decided that Stoltz just wasn't funny enough in the role and was ditched for Michael J. Fox, perhaps it made him learn to lighten up a bit.
8. Mickey Rourke learned to speak Russian for Iron Man 2, virtually all of it gets cut
During Mickey Rourke's brief post-The Wrestler career resurgence, he joined the MCU, bringing along his Oscar-winning approach to play Russian Iron Man villain Whiplash.
Rourke acquired a Russian tutor and spent three hours a day learning the language, as well as visiting a Russian prison to meet some of the inmates in preparation for the role.
The executives at Marvel didn't care for Whiplash's Russian and cut most of Rooney's Russian dialogue from the film and the actor wasn't best pleased when he discovered this:
“[It’s] f*cking too bad, but it’s their loss. If they want to make mindless comic book movies, then I don’t want to be a part of that." He remarked
"You know, I didn’t work for three months on the accent and all the adjustments and go to Russia just so I could end up on the floor."
Here is a 19-second video of all of Rooney's Russian lines in the final film, but unlike some of the people on this list at least he's come away with a new skill.
7. Ashton Kutcher is hospitalised trying to follow Steve Jobs' for the biopic that no-one watched
In a bid to beat Michael Fassbender and deliver a better onscreen version of Apple's iconic co-founder, Ashton Kutcher tried to be as Steve Jobs-like as possible.
Kutcher pored over hundreds of hours of videos tape to replicate Jobs' hunched walk and mannerisms, and even took up his reported fruitarian diet.
Kutcher dined on a strict diet of fruit, nuts and seeds, and just days before Jobs was due to start shooting, was rushed to hospital with pancreatitis.
Was it worth it? Not at all, Kutcher's biopic boasts a paltry 28% rating on Rotten Tomatoes, meanwhile Fassbender's version is rated at 85% and holds a bunch of award nominations and wins.
6. Sylvester Stallone gets fat to star in a film that derailed his career for eight years
Back in the '90s, Sylvester Stallone wanted more to his career than being a one-dimensional muscle-bound punchy chap so attempted to add some diversity to his roles, and one well-worn path to acting credibility is to put on vast amounts of weightfor a film role.
Putting aside his human growth hormones, Stallone gained 40lbs to play a small-town Sheriff in 1997's Cop Land, a crime thriller about mob corruption in the NYPD.
Joining a cast including Harvey Keitel, Ray Liotta and Robert De Niro - what could fail for the Rambo and Rocky star?
Lots, it would seem, despite the film gaining good reviews, grossing a respectable $44 million and Stallone's performance praised, Cop Land just couldn't live up to the Goodfellas-levels of expectations that was placed on it.
Stallone revealed in a radio interview that, with the film failing to reach expectations and him attempting character-driven roles, he had trouble getting film roles for eight years after Cop Land's release.
5. Matthew Fox gets ridiculously ripped for second billing in a terrible movie
The internet was shocked when they saw pictures of Matthew Fox as his character Picasso in Alex Cross.
The Lost star went on a serious diet and training regime to play a cage fighter and serial killer in the adaptation of the popular James Patterson book series.
Unfortunately for Fox, Alex Cross didn't earn back its $35m budget, and was given a staggeringly poor 12% rating on Rotten Tomatoes, which was a waste of all the hours spent working out and not eating nice foods.
4. Taylor Kitsch almost has a breakdown to play a suicidal photographer
While not a major Hollywood player, no-one can claim that Taylor Kitsch went into the biopic The Bang Bang Club in a half-hearted manner.
To play South African photographer Kevin Carter, the Canadian actor went on a strict diet to lose 30 pounds of muscle in two months to match Carter's slight frame.
Kitsch's dedication to his weight loss caused him kidney problems and also sent him into counselling due to the experience; which served the character well as the real Kevin Carter was suicidally-depressed.
Kitsch's efforts weren't really worth it, as The Bang Bang Club flopped financially and critically, while the actor moved on to John Carter which went on to become Disney's biggest movie flop to date.
3. Joaquin Phoenix spends a year pretending to go mad for a film that grossed half a million dollars
No-one is still entirely sure whether Joaquin Phoenix's 2010 mockumentary I'm Still Here is a comedy film, or a film that takes itself so seriously that it has devolved into self-parody.
On a 2009 appearance on the Late Show with David Letterman, Phoenix turned up as an unkempt shambles, telling Letterman that he would be retiring from acting and pursuing a hip-hop career instead.
What hit the screens in 2010 was his year-long endeavour to start a hip-hop career with generous helpings of male nudity, cocaine and general unwatchable drivel.
The drivel was so unwatchable that not many people paid to watch it, as the film raked in a worldwide gross of just $568,963, which was one-tenth his reported salary from starring in The Village.
2. 50 Cent shocks the world with his weight loss for a film that the world didn't care about
In his previous film roles such as Get Rich or Die Tryin' and Gun, muscle-bound rapper 50 Cent played gun-wielding gangsters, similar to the rap persona he portrays.
So the world was shocked when 'Fiddy' posted a selfie of himself looking incredibly skinny, having lost all of his muscles to play a former American Footballer player suffering with cancer in All Things Fall Apart.
The rapper went on a nine-week liquid diet and ran on a treadmill for three hours a day to lose his muscular frame, dropping from 214lbs to 160 lbs - losing nearly four stone in the nine weeks.
Despite 50 Cent's best efforts to lose all the weight, the direct-to-DVD All Things Fall Apart went virtually unnoticed, and despite a somewhat reasonable 58 per cent Rotten Tomatoes rating, the only thing the film is remembered for is 'that film which 50 Cent lost all the weight for'.
1. Jared Leto put on so much weight for a film that no-one has heard of that he got gout
Jared Leto is not a man who acts in half measures, cinemagoers marvelled at his weight loss to play a transgender woman with HIV in Dallas Buyers Club, while stories of him terrorising his Suicide Squad co-stars in preparation to play The Joker are widely-publicised.
Not widely-publicised, however, is Leto's film Chapter 27 in which he put on four and a half stone (67lbs) to play portly John Lennon killer Mark Chapman.
Determined to do it in the most horrible sounding way, Leto would melt down pints of ice cream in the microwave, add olive oil and soy sauce and drink them like shakes - which gave him gout and left him confined to wheelchair.
The finished film recounting the murder of John Lennon was truly terrible, it grossed $187,488 at the box office, and has a dismal 19% rating on Rotten Tomatoes - Leto was so upset that everyone thought his terrible movie was terrible that he didn't act in another movie for six years.