From Charlize Theron to Colin Farrell: The astonishing transformations stars have undergone for the big screen

Over the years, we've seen some stars pour everything they have into their movie roles.

This has often involved some of the biggest names completely transform before our eyes for roles – including the likes of Demi Moore, Charlize Theron, Tom Hanks and Colin Farrell

Read on to see some of the biggest on-screen evolutions we've ever seen.

Watch the videos above.

Demi Moore in G.I. Jane

These days, Demi Moore is known for her signature long, jet black hair.

But the American star, now 63, famously shaved her head for her role in the 1997 action flick G.I. Jane. The film was directed by Ridley Scott and co-starred Viggo Mortensen.

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However, Moore failed to win critical acclaim for the role and instead reportedly got a Razzie Award for Worst Actress.

Reflecting on shaving her head, she told People she takes care of her hair now and won't be shaving it or chopping it anytime soon.

"I think now that I'm older, I also know I don't have anything to prove. So if they really need my hair different, they can give me a wig."

Charlize Theron in Monster

Who could forget this one?

Theron is one of the most stunning stars in Hollywood, but was completely unrecognisable as she transformed for her role in Patty Jenkins' 2004 thriller Monster.

She played Aileen Wuornos, a late American serial killer.

For the role, the actress shaved her eyebrows and put on 30 pounds (13.6kg).

The role nabbed Theron an Academy Award for Best Actress.

You can't say she's not committed to her craft – she later shaved her head for Mad Max: Fury Road.

Tom Hanks in Cast Away

The hit 2000 film Cast Away starred Tom Hanks as we've never seen him before.

The actor completely transformed into his character Chuck Noland, who gets deserted on an Island and leans on a volleyball he calls Wilson as a friend.

He reportedly lost up to 25kg for the film and grew out his hair and beard.

According to reports, production was paused for a year for Hanks to transform and lose weight.

He has type 2 diabetes and previously said, according to The Guardian, that he has no plans to dramatically transform himself for another role at his age.

"I've talked to a number of actors who have gained weight for roles, and just the sheer physical toll it puts on one's knees and shoulders – no one wants to do it again," he said.

"I'm 57 and I don't think I'm going to take on any job or go on vacation again and see to it that I can gain 30 pounds."

Colin Farrell in The Penguin

Colin Farrell is a Hollywood hunk, but he looks worlds away from his usual self in the crime show The Penguin.

The specialist makeup team used prosthetics on the actor, 49.

Prosthetic makeup designer Mike Marino told Forbes: "On the technical end, we really developed a new kind of a silicone, which varies in densities and thickness.

"It was like many different variables of skin, like it was created by God."

"It's a real constant effort to bring this character to life."

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