As we are fond of pointing out, sometimes the most convicing performances you see in movies aren't skillful acting at all, but genuine moments of humiliation, terror, and/or insanity:
  1. Channing Tatum in 'Foxcatcher'
    After a few bad takes of a fake slap in the movie, Channing Tatum lost his cool with Mark Ruffalo and shouted "C'mon man, I'm trying to act here. What is that? Come on! Be a man! Hit me!" Ruffalo didn't hold back the next time, and slapped Tatum so hard that he broke his eardrum, because that's what happens when you yell at the goddamn Hulk. In another scene, Schultz loses his temper and smashes his face into a mirror. It wasn't scripted, and Tatum smashed it so hard he broke drywall behind it.
  2. Mickey Rourke in 'The Wrestler'
    There are several scenes where Rourke's character Randy "The Ram" Robinson and his fellow performers smuggle razor blades into the ring to cut their faces open. Rourke got himself so invested in the role that when that big scene came up, he pulled a concealed razor blade from his wrist straps and slashed his forehead open like Freddy Krueger popping a zit. After the scene was over, the real wrestlers hired for the film gave Rourke a standing ovation for treating their industry with respect.
  3. Linda Hamilton in 'Terminator 2'
    One early scene called for an asylum orderly to beat the hell out of her, but the actor kept pulling his punches because he didn't want to really harm Hamilton. But that meant every time he flailed pathetically at Hamilton, she had to fall to her knees on the hard concrete, and the scene had to be reshot again and again, hurting Hamilton's knees, pissing her off. So In a later scene, where Sarah Connor attacks that orderly character with a mop handle, Hamilton did it for real.
  4. That extra in 'The Wolf Of Wall Street'
    Martin Scorsese hired a woman to have her head shorn completely on camera. The woman was Natasha Newman Thomas -- who was not an actress, but a hairstylist and costume designer who happened to be friends with Leonardo DiCaprio. Being a hairstylist, Thomas naturally had major reservations about having her hair chopped off for the sake of the longest frat comedy ever filmed, but she eventually agreed to it.
  5. Nicole Kidman and Zac Efron in 'The Paperboy'
    Efron's character is swimming at the beach when he gets stung by jellyfish, and a couple of girls nearby come to his rescue, believing that the best remedy is to have someone pee on his wound. And according to everyone involved, there was no tube of prop urine or CGI -- they straight-up had Nicole Kidman piss on him.