Eddie Redmayne, Jared Leto, Matthew McConaughey and Natalie Portman have all changed their look for their art - and some celebs just do it for a bit of fun...
It's a time-honoured tradition in Hollywood that the more dramatic the makeover an actor undergoes for a role, then more often than not, Oscar success follows suit.
Whether it's through insane workouts, crazy diets or hours spent in the hair and make up chair, the great and the good of the silver screen have been undergone some very impressive transformations to look like the character they're portraying
Nicole Kidman donned a prosthetic nose to play Virginia Woolf in The Hours and looked utterly different despite the less dramatic, physical transformation.
You might also remember when Natalie Portman shaved her head in the mid Noughties for her part in V For Vendetta and famously debuted her new 'do at the Cannes Film Festival.
Meanwhile, Glenn Close totally transformed herself to play Albert Nobbs, a woman living as a man to become a butler, spending two hours a day in prosthetics. And who can forget, Charlize Theron's Oscar-winning portrayal of serial killer Aileen Wuornos in Monster, where she gained over two stones for the part as well as spending hours in the make-up chair on set.
Jake Gyllenhaal transformed himself into a boxer for Southpaw, and his fitness regime was pretty intense by all accounts; the actor reportedly worked out for an absolutely bonkers six hours a day to get his ripped new body.
And who can forget Matthew McConaughey's shocking weight loss for The Dallas Buyer's Club?
Tilda Swinton
First up though and Tilda Swinton - who is no stranger to a movie makeover or two (you've seen Trainwreck, right? - looked worlds apart from her usual achingly stylish self when she stepped out on the NYC set of Okja in July 2016...
Tilda Swinton
First up though and Tilda Swinton - who is no stranger to a movie makeover or two (you've seen Trainwreck, right? - looked worlds apart from her usual achingly stylish self when she stepped out on the NYC set of Okja in July 2016...
Tilda Swinton
For her new role, the Brit actress swapped out her trademark cropped hairstyle for a bob and lashings of eyeliner.
Read on for more jaw-dropping on-set makeovers...
Meryl Streep
It's a time-honoured tradition in Hollywood that the more dramatic the makeover an actor undergoes for a role, then more often than not, Oscar success follows suit.
Whether it's through insane workouts, crazy diets or hours spent in the hair and make up chair, the great and the good of the silver screen have been undergone some very impressive transformations to look like the character they're portraying
Nicole Kidman donned a prosthetic nose to play Virginia Woolf in The Hours and looked utterly different despite the less dramatic, physical transformation.
You might also remember when Natalie Portman shaved her head in the mid Noughties for her part in V For Vendetta and famously debuted her new 'do at the Cannes Film Festival.
Meanwhile, Glenn Close totally transformed herself to play Albert Nobbs, a woman living as a man to become a butler, spending two hours a day in prosthetics. And who can forget, Charlize Theron's Oscar-winning portrayal of serial killer Aileen Wuornos in Monster, where she gained over two stones for the part as well as spending hours in the make-up chair on set.
Jake Gyllenhaal transformed himself into a boxer for Southpaw, and his fitness regime was pretty intense by all accounts; the actor reportedly worked out for an absolutely bonkers six hours a day to get his ripped new body.
Take for instance, Meryl Streep. The Meryl that we know and love is always looking chic and elegant...
Meryl Streep as Donald Trump
But things were different at the Park Public Theater Gala at the Delacorte, Oscar winner Meryl Streep teamed up with Christine Baranski to perform 'Brush Up Your Shakespeare' from Kiss Me, Kate. Our much-loved Meryl was looking a little different though, having swapped out her chic red carpet look for an oversized suit, terrible fake tan and blonde mop. Hey, it's Donald Trump! Excellent work, Meryl.
Kardashian-Jenners
The Kardashian-Jenners look like this normally.
Kylie Jenner
For Kylie Jenner's Snapchat followers, fans were treated to a bizarre but kind of hilarious attempt at a disguise, when Kylie, Kendall and Khloe all donned prosthetics to fool some unsuspecting tourists.
Kendall Jenner
Kendall looked unrecognisable with a prosthetic nose and huge mane of ginger hair masking her signature brunette locks.
Khloe Kardashian
And Khloe rounded out the trio in perhaps the best disguise of the day, with a grey bob wig and prostethic chin to give you that older look. Hilarious.
Chris Hemsworth
This is Chris Hemsworth as we're used to seeing him: buff, handsome and absolutely nothing like he looks in his latest movie transformation...
Chris Hemsworth
For his new movie, In The Heart Of The Sea, Chris Hemsworth lost a ton of weight by sticking to a strict 500 calorie-a-day diet - and shared the evidence on his Instagram, writing: 'Just tried a new diet/training program called "Lost At Sea". Wouldn't recommend it..'
Matthew McConaughey Golden Globes
Matthew McConaughey is no stranger to transforming for a role. He dropped a drastic amount of weight for his Oscar winning performance in The Dallas Buyers Club but it looks like he's gone the other way for his latest movie...
Matthew McConaughey Gold set
The 45-year-old was barely recognisable when he was spotted in New York filming his latest movie, Gold. Texan Matthew was sporting a balding head, rather portly tummy and a godawful brown suit for his turn as a down on his luck business man in the 80s who decides to go trekking in the jungles of Indonesia to find gold.
Elle Fanning
Elle Fanning's next role calls for a total make-under. The usually glossy glam starlet plays a teenager called Ray, struggling with her transition from female to male...
Elle Fanning In About Ray
Elle ditches her red carpet gowns and trademark blonde waves for baggy clothes and a new crop. With Naomi Watts playing Ray's mother and Susan Sarandon playing his lesbian grandmother, we can't wait for About Ray to hit cinemas in September 2015.
Eddie Redmayne
Eddie Redmayne's next big role in The Danish Girl calls for a complete transformation. Playing Lili Elbe, one of the first people to ever undergo gender reassignment, you absolutely will not recognise the Oscar winning actor...
Eddie Redmayne In The Danish Girl
...We told you so. How incredible do Eddie's cheekbones look in this promotional shot?! We can't wait for the film to be released in January 2016, just in time for awards season. Could this transformation bag Oscar number two for Mr Redmayne?
Eddie Redmayne In The Theory Of Everything
And let's not forget Eddie Redmayne's first major movie transformation, playing professor Stephen Hawking in 2014's The Theory Of Everything. The star worked with a choreographer to capture ALS sufferer Stephen's physical conditions.
Tilda Swinton
In July 2015, Tilda Swinton looked totally differed from her usual, ethereal self as a magazine editor in Trainwreck. Warning: You may not even recognise her...
Tilda Swinton In Trainwreck
Yes, this is Tilda Swinton.
Gone is her elfin platinum hair and barely-there makeup - say hello, instead, to a deep tan and the perfect bronde hair extensions. According to reports, the actress spent an hour a day fake tanning, followed by "layers and layers" of bronzer to achieve this look for the movie which sees her play a magazine editor, no less.
We hardly recognised her when we saw Trainwreck - and that's the mark of a great transformation!
Jake Gyllenhaal
Here's Jake Gyllenhaal looking suited and booted on the red carpet...
Jake Gyllenhaal In Southpaw
And pep, this is actually Jake Gyllenhaal, too. The actor transformed himself into a boxer for Southpaw, and his fitness regime was pretty intense by all accounts; the actor reportedly worked out for an absolutely bonkers six hours a day to get his ripped new body.
"I knew nothing about boxing when I started really," he told Entertainment Tonight. "I knew that in order for me to pull it off in any way, I was just going to have to learn how to do it.
"When I set my mind to something I just won't stop until I do it. It's something I pride myself on. It's something I hate about myself. By the end I felt like I could do it.?
Nicole Kidman
Nicole Kidman on the red carpet as we know and love her...
Nicole Kidman in The Hours
But for her role as English writer Virginia Woolf in The Hours, Nicole was barely recognisable thanks to facial prosthetics and a long, brunette wig.
Rooney Mara
Rooney Mara's red carpet style is an inimitable mix of polished and bang-on-trend.
Rooney Mara in The Girl With The Dragon Tattoo
But Rooney looked quite different in the big screen adaptation of The Girl With The Dragon Tattoo thanks to dying her eyebrows blonde and getting several piercings to play Lisbeth Salander - including her nipple!
Natalie Portman
Natalie Portman has undergone a few transformations for her big screen outings...
Natalie Portman in V For Vendetta
And despite undergoing quite the makeover for the Oscar-winning Black Swan, her most dramatic transformation for the silver screen has to have been when she shaved her head for her role as Evey in V For Vendetta.
Charlize Theron
An ambassador for Dior, former model Charlize Theron never fails to impress on the red carpet...
Charlize Theron in Monster
But like all actors worth their Hollywood salt, Charlize underwent one of the most startling transformations for her role as serial killer Aileen Wurnos in Monster. Barely looking like herself at all, Charlize did end up bagging the Best Actress Oscar for her performance.
Glenn Close
Award-winning actress Glenn Close has been nominated for six Oscars so we know she's committed to her art...
Glenn Close in Albert Nobbs
She spent two hours in makeup to play the titular role of Albert Nobbs, a woman living as a man in the Victorian era.
Anne Hathaway
Both on and off screen, Anne Hathaway knows how to bring the glamour...
Anne Hathaway in Les Miserables
But as improverished Fantine in Les Miserables, Anne's long brunette hair was chopped off live on screen in the movie and she lost a staggering stone and a half for the role.
Jared Leto
A snappy red carpet dresser with enviable ombre locks, it almost feels like Jared Leto hasn't aged since his debut TV appearance in My So-Called Life all those years ago.
Jared Leto in Chapter 27
But for his role as Mark Chapman in Chapter 27, Jared gained an unbelievable four-and-half stones and has since revealed that his changed diet resulted in him getting gout.
Cameron Diaz
Cameron Diaz is red carpet royalty and mostly sports a choppy blonde 'do.
Cameron Diaz In Being John Malkovich
However, in Being John Malkovich, Cameron donned a frizzy mousy brown wig and managed to look almost entirely different to the Ms. Diaz we know.
Matthew McConaughey
Matthew McConnaughey was known for being super-fit before he underwent an incredibly dramatic transformation for his role in Dallas Buyers Club.
Matthew McConaughey In Dallas Buyers Club
McConaughey lost a scary amount of weight to play an AIDS patient in the film (an absolute must-see if you have yet to watch it) and of course, won the much-deserved Best Actor Oscar for it too.
Tom Hanks
Ah, the lovely Tom Hanks.
Tom Hanks In Cast Away
But to play Chuck Noland in Castaway - of which his portrayal of the FedEx exec marooned on an island snagged him an Oscar - Hanks lost just shy of four stones.
Tom Hardy
Suited and booted on the red carpet, although Tom Hardy has a (much-admired) athletic physique, his physical transformation for the part of Bane in the Batman franchise was nothing short of frightening.
Tom Hardy In The Dark Knight Rises
Yikes.
Christian Bale
Consumate actor Christian Bale is a slave to his art but arguably never more so than when he prepped for his role in The Machinist.
Christian Bale In The Machinist
Yep, Christian lost a frighteningly dramatic four stones for the role.
Hilary Swank
Hilary Swank's Oscar winning roles have seen the actress transform herself for her roles over the years...
Hilary Swank In Million Dollar Baby
For her portrayal as boxer Maggie Fitzgerald in the the heart-breakingly moving Million Dollar Baby, Hilary Swank trained like a pro building a hard-won athletic physique for the movie.
Renee Zellweger
And how could this list not include master of the transformation, Renée Zellweger?
Renee Zellweger In Bridget Jones' Diary
Bringing Helen Fielding's beloved literary heroine Bridget Jones to the big screen in 2001, Renée put on a bit of weight for the role but still looked utterly gorgeous. Plus, she's a forever idol in our eyes after looking so good in "granny pants".