Part of what makes film so extraordinary is the transformations that actors undergo in order to fully become their characters. Actors' physical transformations allow audiences to completely rid these actors' previous roles from memory, and can transport them into a new film, watching the actor as if for the first time. Over the years, several well-known actors have endured extreme transformations for particular roles, wowing audiences with their drastic transition from their normal selves.

Johnny Depp in Black Mass

Johnny Depp in Black Mass

Critics and audiences alike are buzzing over Johnny Depp's unrecognizable self in his portrayal of gangster Whitey Bulger in the upcoming film Black Mass, as his dark locks are dyed white-blonde and he dons coloured contacts to depict the Irish-American Boston mobster. In honour of the upcoming release of Black Mass, take a step back in time to look at some of the most iconic movie transformations ever.

- Christian Bale - The Machinist

Christian Bale is an actor known for his commitment to his character, and over the years has become a yo-yo dieter in order to look the part for several films. In his role in the 2004 psychological thriller The Machinist, Bale dropped 60 pounds to look the part of his character, Trevor Reznik, a factory worker who becomes emaciated as a result of his insomnia.

Prior to filming, Bale dieted for four months in order to look the part of Reznik. The 6-foot actor dropped to roughly 120 pounds, and despite his desire to lose even more, filmmakers put a stop to his weight loss for fear of health concerns. It was recently discovered that it was never intended for Bale to drop all the weight.

A typo in the script depicted the much shorter director's height and weight, but Bale wanted to see if he could still lose the weight. Bale's sickly and almost unrecognizable appearance in The Machinist is just one example of his drastic commitment to his onscreen transformations.

Bale then had to pile all the weight back on as he prepared for his role as Bruce Wayne in Batman Begins. We have also seen him drop weight for roles in Rescue Dawn and The Fighter; the latter saw him win a Best Supporting Actor Oscar.

The Machinist

- Charlize Theron - Monster

Charlize Theron's performance and transformation into former-prostitute-turned-serial-killer was one of her most remarkable transformations to date. In the movie, Theron depicted Aileen Wuornos, a former prostitute who was sentenced and killed by lethal injection in the early 2000s after she killed six men in the late 1980s and early 1990s, clients who she was convinced were going to rape her.

In preparation for the role, Theron gained access to letters Aileen wrote to a friend over a twelve-year span, granting her insight into the mindset of Aileen. Through video footage of Aileen, Theron learned to walk like Aileen and pick up her mannerisms and various behaviours. Theron's transformation into Aileen was so incredible that she won the Academy Award for Best Actress in a Leading Role for her role in Monster.

Theron's physical transformation was just as important as her acting performance that ultimately led to her Oscar win. In order to get into character and attempt to portray a mentally ill woman with borderline personality disorder, Theron gained thirty pounds prior to the film, and shaved her eyebrows.

To look more like Aileen, Theron wore prosthetic teeth, and critics noted that her makeup and unrecognizable features helped accentuate her performance. Theron claims that this role broke her out of a rut, one in which she was constantly typecast as the 'sexy blonde,' proving Monster to be her biggest breakthrough and transformation at the time.

Monster

- Hilary Swank - Boys Don't Cry

Hilary Swank was virtually unknown when she was cast in the 1999 film Boys Don't Cry, a film based on the true-life story of Brandon Teena, a trans-man who struggled to live a normal life and find acceptance in his community. Brandon was 21 years old when he was brutally raped and murdered by two male friends, and after his death made national news, LGBT advocacy was brought to the forefront. Boys Don't Cry was a tribute to Teena, and an attempt to raise awareness surrounding violence towards LGBT persons.

When Swank was cast as Brandon, she immediately chopped her hair off and dyed it dark brown and in order to prepare for filming, she spent several months dressing and living life as a man, even convincing neighbours that she was Swank's brother. Swank wrapped bandages around her chest, and put socks down her pants, trying to fully emulate the everyday life that Brandon Teena led. Swank even dieted for months in order to reduce her body fat to roughly seven percent so her facial structure would appear more accentuated.

During the filming of Boys Don't Cry, Swank refused to have any cast or crew see her outside of costume, to ensure her portrayal of Brandon was as convincing as possible. Hilary Swank's major transformation and outstanding portrayal landed her an Academy Award for Best Actress in a Leading Role.

Boys Don't Cry

- Elizabeth Banks - The Hunger Games

When Elizabeth Banks landed the role of Effie Trinket in the film series based on the widely popular Hunger Games book trilogy, she knew her transformation would be extreme. Effie (Banks) is the PR mentor for Katniss Everdeen, the Hunger Games tribute from District 12.

As a citizen of the 'capital' of the twelve districts, Effie's appearance is colourful in both her bold personality and outrageous style. Members of the capital 'express themselves through hair, makeup, and clothes,' Elizabeth Banks has said during interviews, and her transition into Effie was no exception.

Banks spent three hours every day getting into makeup, and by the end, was unrecognizable as her character. Constantly covered in giant coloured wigs, frosted lips, long nails, eccentric makeup, and outrageous outfits, Banks underwent a vibrant transformation.

The Hunger Games

- Rooney Mara - The Girl With The Dragon Tattoo

When The Girl with the Dragon Tattoo - based off of Swedish author Stieg Larson's book of the same name - was made into a major motion picture, no one was able to recognize Rooney Mara in the leading role. In The Girl with the Dragon Tattoo, Mara portrays Lisbeth Salander, a punkish tomboy computer hacker who has been physically and emotionally damaged from sexual abuse.

Mara's unrecognizable appearance was due to her immense physical transformation leading up to the film. Mara's hair was dyed black, and her uneven locks were meant to give the appearance that she cut her own hair. Mara's eyebrows were bleached, and she got several piercings in order to look the part of Lisbeth.

Prior to filming, Mara even moved to Stockholm by herself in order to understand her character even better. Noting that she was meant to look like a '14-year-old boy,' Mara explained that her year-long portrayal as Lisbeth allowed her to fully transform, both physically and mentally, into her role.

The Girl With The Dragon Tattoo

- Tom Cruise - Tropic Thunder

When Tom Cruise originally received the script of the 2008 satirical action comedy Tropic Thunder, he felt as though something was missing from the film. Cruise suggested to writer/director/producer Ben Stiller to add an additional character to the film to make it feel more complete, and the two worked together to create the pig-headed, unlikeable, Les Grossman, the studio head that everyone loves to hate.

It is hard to tell from watching Tropic Thunder that Tom Cruise is the man behind Les Grossman. Yes; the balding, overweight, and greedy studio executive is actually Tom Cruise underneath mass amounts of makeup. Donning a fat suit, a bald cap, extra hairy arms, and fake large hands, Cruise looks a different person altogether.

Tropic Thunder

- Eddie Murphy - The Nutty Professor

The wildly funny Eddie Murphy is known for his iconic role in the 1996 film The Nutty Professor, a comedy about Sherman Klump, a loveable professor who is exceedingly obese. Murphy plays seven different characters throughout the film, and all of whom are truly memorable for their boisterous and over the top personalities.

Sherman (Murphy) constructs a scientific formula that allows people to lose weight, and after testing it on himself, loses hundreds of pounds in a matter of seconds. The newly skinny Sherman disguises himself as the confident Buddy Love (also played by Murphy), and continues to chase after the girl he loves.

Throughout the film, Murphy portrays Lance Perkins, a parody of Richard Simmons, as well as all of Sherman's family members, including Granny Klump, Mama Klump, Papa Klump, Young Papa Klump, and Ernie Klump, all of whom appear together in a hilarious family dinner date scene in the film. Murphy's talent and comedic variety in his portrayal of these seven characters has made The Nutty Professor a classic and is one of his biggest transformative roles to date.

The Nutty Professor

- Mariah Carey - Precious

When Mariah Carey first appeared onscreen in the 2009 film Precious, audiences were shocked to see her 'de-glamed' transformation. As someone who is known for her glamour, beauty, and 'diva' status, Carey admits her transformation in Precious was difficult for her.

Carey portrays Ms. Weiss, the drab welfare case worker who is empathetic towards Precious and attempts to help turn her situation around. Carey claims she had to 'lose all vanity' for the film, and accept all her flaws. She appeared totally different from the made-up woman we know her as, donning no makeup, dark bags under her eyes, and even a bit of a moustache throughout the film.

However uncomfortable she was with her appearance during filming, though, is unclear through her portrayal of Ms. Weiss onscreen. Though her role is a fairly minor one, Carey brings about a powerful and emotional performance of a woman trying to help a troubled teenage girl in Precious, and her serious make-under and powerful performance cannot go unnoticed.

Precious

- Heath Ledger - The Dark Knight

Heath Ledger has become known worldwide for his role as the Joker in the film The Dark Knight, the second instalment of the Batman trilogy. Shortly before the film's release, Ledger was found dead of a presumed accidental drug overdose, and posthumously received an Academy Award for Best Supporting Actor for his portrayal of the Joker.

Ledger himself described the Joker as a 'psychopathic, mass murdering, schizophrenic clown with zero empathy,' and leading up to filming, Ledger spent six weeks locked away in a hotel room, isolating himself to fully immerse himself into the role of the Joker. During that time, Ledger wrote in a character diary which contained pictures of clowns and comic books, scribbles with the Joker's thoughts, and chaotic ideas that the character would find funny. Ledger used this time to experiment with voices in order to perfect the voice and laugh that he felt was necessary for a maniacal killer to have.

Physically, Ledger's transformation on screen rendered him unrecognizable. Donning a full face of clown makeup, Ledger's black eyes and scarred cheeks were meant to show the Joker's dirty and sweaty appearance, and his streaked makeup and dirty hair helped transform Ledger into the serial-killing clown that he has become so well known for.

The Dark Knight

- Matthew McConaughey - Dallas Buyers Club

In order to take on the role of an HIV-positive cowboy Ron Woodroof in the 2013 film Dallas Buyer's Club, Matthew McConaughey underwent some serious transformations. McConaughey spent four months dieting in order to shed 47 pounds for his role. McConaughey met with a nutritionist to lose the weight in what he refers to 'as healthy a way I found possible,' and lost roughly three and a half pounds every week.

Beyond the physical transformation, McConaughey watched footage of Ron Woodroof's interviews with screenwriter Craig Borten from 1992 and met with members of Woodroof's family, who granted him access to Ron's diary from the years before he was diagnosed with HIV.

This gave McConaughey insight into Ron's life as a 'normal guy' before his 1985 diagnosis, which helped create a voice through which McConaughey could portray Woodroof. McConaughey's transformation - both physically and mentally - paid off, because he won the Academy Award for Best Actor in a Leading Role for his portrayal in Dallas Buyer's Club.

Dallas Buyers Club

- Johnny Depp - Black Mass

Johnny Depp often undergoes major transformations to portray a character, but most often audiences can still make out the actor beneath all the makeup. However, in the upcoming film about the life of Boston's most notorious gangster, Johnny Depp is almost unrecognizable due to the drastic alternations in his appearance.

In the soon-to-be-released film Black Mass, Depp portrays Whitey Bulger, the Irish mobster who spent several years on the FBI's Top Ten Most Wanted List while he was on the run from the law. To prepare for the film, Depp underwent several startling transformations. Depp's familiar deep and raspy, whispering voice is gone, swapped for a thick Boston accent. His signature dark hair and brown eyes are gone as well, replaced by a balding head of white-blonde hair and coloured contacts to parallel Bulger's blue-eyed, blonde-haired, Irish complexion. The result is a man that does not resemble Depp at all.

To get into character, Depp's hair was blow dried flat and then capped so makeup artists could put the prosthetic and hairpieces on his head. Once fitted, hair was punched into the silicone forehead, a process that took roughly twenty-two hours to complete. An entire prosthetic covered Depp's face, from his nose to the middle of his head. False eyebrows were attached, and Depp wore coloured contacts to recreate Whitey's signature piercing blue eyes.

Depp watched hours of footage where he could hear Bulger's voice, in order to capture Whitey's 'true, animalistic behaviour,' and reached out with the hopes of speaking with Bulger personally in prison, but was turned down. Depp's utterly unrecognizable physical transformation, as well as his mesmerizing performance, are one of Depp's most shocking transitions to date and are sure to make Black Mass a box-office success.

Black Mass

Black Mass is released 25th November.