Scarlett Johansson almost "knocked out" a stuntman during a fight scene in 'Ghost in the Shell'.
The 32-year-old actress' powerful performance as The Major was quite "frightening" to the cast and crew on the film, and director Rupert Sanders was in awe of her physical abilities.
Rupert said: "She is tough and when she is beating the s**t out of someone is quite frightening. She is able to pull a punch within about 3mm and that is quite a shocking thing to see.
"[In the] water courtyard fight, Scarlett was so in the rage - punch, punch, punch - that when we cut the stuntman was like, 'You almost knocked me out!' And she was like, 'Did I?' She hadn't even realised."
And Rupert was impressed by the physical transformation Scarlett underwent to prepare for the role.
He said: "Scarlett was in the gym every morning way before we all got to set and her body was really transformed into the Major.
"When you see the shots from behind, her back in just rippling with muscle that is so reminiscent of the character in the anime.
"She had a team of martial arts and military trainers who she worked with every day.
"She got to a level physically where she carried that confidence and it really showed in her performance."
If the movie does well, a sequel is likely to be in the works, a prospect Scarlett finds "daunting" but is also excited about.
She told SciFiNow magazine: "That is daunting because it is not totally obvious what the next chapter is for this character.
"It is also physically daunting. This film was extremely draining, physically, emotionally, and professionally and it required an immense amount of discipline and thought.
"But of course, the idea that this female-driven genre film could go on to have a sequel, and that it could be successful enough to demand a sequel is very exciting.
"It would be a real victory in many ways. I am up for the challenge.
"I am a big girl. I can handle it. I think."