Method acting is a series of techniques that sees performers draw on their emotions and personal memories to enhance the realism of their roles. But this is merely a jumping-off point for some actors. Specifically, folks whose quest for authenticity leads to pretty darn hardcore physical and psychological transformations. Here are five fantastic roles made possible by A-list thespians who took ‘the method’ to the extreme.

Jim Carrey — ‘Man on the Moon’

As one of his first dramatic films,  Man on the Moon saw Jim Carrey go double duty as quirky actor/comedian Andy Kaufman and his even quirkier alter ego Tony Clifton. So bent on perfection, J.C. remained in character for the duration of the shoot (several months!), alienating friends, family, and even strangers in the process.

Robert De Niro — ‘Raging Bull’

To get into the head — and physique — of boxer Jake LaMotta, Robert De Niro pushed himself to the limit. First by transforming himself into a prizefighting pugilist: bulking up with pure muscle, training for months, and even competing in several organized bouts. He followed this up by slapping on 60 pounds of fat (to play the later-era LaMotta), a move that lead to serious health issues throughout the early 1980s. But hey, he nabbed an Oscar for the role, so there’s that.

Daniel Day-Lewis — ‘My Left Foot’

Speaking of Oscar-winning roles, Daniel Day-Lewis took home a little gold statue for his portrayal of cerebral palsy sufferer slash acclaimed writer Christy Brown. But that road to the victory podium was paved with a whole lot of sacrifices. Day-Lewis insisted on staying in character off camera, which meant a contorted body position and very limited physical movement. As such, members of the film crew needed to wheel him around, lift him in and out of his chair, and yep, even feed him. The eccentric Irishman even broke several ribs due to the physical toll the character took on him.

Heath Ledger — ‘The Dark Knight’

When it was announced young, hunky Aussie Heath Ledger would take on the iconic role of The Joker in The Dark Knight, more than a few critics needed convincing he had the chops to pull it off. In retrospect, their skepticism seems absurd. To prepare for what became his Oscar-winning performance, Ledger locked himself in a hotel room for a month, taking his psyche to the breaking point by filling copious notebooks with dark, deranged musings. Many believe this contributed to the the insomnia that played a role in his untimely demise.

Christian Bale — ‘The Machinist’

And speaking of insomnia, Christian Bale dropped an astounding 120 pounds to play sleep-deprived industrial worker Trevor Reznik in The Machinist. And yes, this may very well be the record for film-related weight loss. Bale doesn’t simply get skinny as the movie runs on — he becomes downright skeletal. His diet for four months: one can of tuna, OR an apple. The end. Alas, despite widespread critical accolades, The Machinist pulled in some seriously skinny box office revenues.