Jennifer Lawrence — Winter’s Bone. She actually learned how to skin and gut a dead squirrel for Winter’s Bone so she could do it on-screen.

Brad Pitt — Fight Club. For Fight Club, he voluntarily had a dentist chip pieces from his front teeth to look like, well, someone who was actually in a fight club. After filming, Brad went right back to the dentist to have them fixed.

Charlize Theron — Monster. To portray serial killer Aileen Wuornos, she shaved her eyebrows, wore prosthetic teeth, and made sure her hair was thinned and repeatedly fried her ends.

Jamie Dornan — The Fall. To get in the right mindset for his role as a serial killer, he admitted to following a woman off the train. He said he kept his distance as he followed her around a couple of street corners and that “it felt kind of exciting, in a really sort of dirty way.” Yeah, he should’ve kept that to himself…

Rooney Mara — The Girl with the Dragon Tattoo (US). Mara went as far as getting her nips pierced to match the character’s description in the book trilogy. And since her character is covered in tattoos and piercings, she also got 4 ear piercings and her lip and nose pierced as well.

Jamie Foxx — Ray. Foxx lost 30 pounds for the role and even wore prosthetic eyelids, which he had glued shut for 14 hours a day. He later admitted to having panic attacks because of it.

John David Washington — Tenet. For the very confusing sci-fi flick, Washington had to do some very confusing things. He not only learned how to talk backward, he was also taught how to walk, fight, block, run and even blink backward.

Nicole Kidman — The Paperboy. Although the myth of peeing on a jellyfish sting to relieve the pain has been disproven MANY TIMES, I guess multi-million dollar films don’t use Google. In this film, Zac Efron’s character is stung by a jellyfish and instead of just faking it, Kidman actually peed on his face. Gross.

Halle Berry — Jungle Fever. To play a crackhead in this Spike Lee joint, Berry admitted to foregoing showering for about eight weeks. Also gross.

Michelle Williams — My Week with Marilyn. In order to accurately capture Monroe’s walk, Williams walked around everywhere with a belt tied around her knees.

Choi Min-sik — Oldboy. One of the many stunts in this movie involved the main character, played by Min-sik, eating a live octopus, and boy did he oblige. In fact, they had to do four separate takes so he ended up eating four. Since he is a Buddhist and a vegetarian, Min-sik apologized to the creature and said a prayer before he put each one in his mouth.

Bryan Cranston — Breaking Bad. Cranston and Aaron Paul were both taught how to make meth by DEA chemists, who were consultants on the show. However, Cranston admitted they didn’t actually straight-up cook the meth, but they were instructed on the detailed process.

Chloë Sevigny — The Brown Bunny. In one of the more dedicated moves, Sevigny chose to actually perform oral on her costar Vincent Gallo, who was also the film’s director and her real-life boyfriend at the time.

Rosamund Pike — Gone Girl. One of the more memorable scenes in the movie consists of Pike’s character seducing her ex and slitting his throat with a box cutter. In order to prepare, she practiced using a box cutter on a pig carcass at a local butcher shop to “understand what it would be like.”

Ruth Wilson — Dark River. For her role as a farmer in this British drama, Wilson decided to work on a farm in Yorkshire to learn the ends and outs of the trade. She learned how to clip feet, shear sheep and castrate lambs.