Before Rosamund Pike was a Gone Girl, she was a Bond girl. Sort of.

The psychological thriller, Gone Girl, directed by David Fincher, is one of our favorites. Nothing is more interesting than a psychotic woman who gets her revenge by framing her husband for murder and then goes M.I.A. until the right moment. Kinda sounds like the plot of The Invisible Man, not going to lie.

How do you get in the head of a killer and make it believable, though?

Pike has some idea but may have taken her method acting a little too far, like a lot of actors do, and looking back she wonders if she was just that bad. Plenty of roles have messed with their portrayer's minds, but playing Amy really affected Pike.

Read on to find out what Pike did to prepare for one of her most famous roles.

The Role Had Her Questioning Her Own Morals

It's crazy when an actor or actress can muster up the temperament of a psycho killer and make it look believable. Could you imagine trying to get into a murderer's mind and becoming them? It can mess with even the best method actors, so Pike had to tread carefully before portraying Amy.

But after a while, Pike herself began to question her own morals and continues to, years after playing Amy.

Related: Does Daniel Day-Lewis Take His Method Acting Too Far?

"Come on, you're playing a sociopath in a convincing way for a number of months," Pike told The Off-Camera Show. "You think that doesn't fuck with your brain? You're like 'Is this because I'm a terrible person? Can I pull this off because I am awful?' Of course, it crosses your mind."

Pike said as an actor you are both pretending and convincing yourself that the role you're playing is real. She really wrestled with that playing Amy. Plus there was all the preparation she had to do to get in that mindset.

For Amy's gory sex/slashing scene with Neil Patrick Harris' Desi, Pike went to a butcher and practiced her slashing on the helpless, yet very dead pigs, using her own box cutter. She and Harris also stripped to their underwear and went to a private soundstage to practice mock-sex for hours, and when that got to be too uncomfortable, she went and got a Dora the Explorer doll of all things to practice on, and placed it on a six-foot stake.

Related: How Anne Hathaway Prepared For Her Role As Catwoman In 'Batman: Dark Knight Rises'

"This isn't even cool, this isn't even method acting," Pike said told Jimmy Fallon. "This is insane."

The author of the book, Gillian Flynn, told Variety that Pike was perfect for the role. "Amy has many sides to her, and Rosamund was able to really show one emotion to the next. It’s a pretty thrilling and frightening talent."

Fincher agreed. "The role is really difficult, and Rosamund was born to play it," he said. He gave her a run for her money as well, with all the takes he wanted. One scene had 18 takes and almost gave Pike a concussion. She also took about 20 showers a day from all the blood.

Related: Here's Why Ben Affleck Was Once Kicked Out Of A Casino

The director knew he had his Amy, though, when he first talked to Pike. "We talked about the transformation," Pike said. "He wanted to see where my vanity lay, and whether I would be prepared to go to some places."

In The Off-Camera Show, Pike was asked whether it worried her at all that Fincher thought she was totally believable as a sociopath. "Yeah, you know that does crop up in one's mind. But I don't know. Sociopaths are very clever, very attractive people."

Pike explained she got this almost nervous energy when Amy was in control of the scene, and Pike knew she was doing it well. "This is such a precariously scary feeling of being convincing in this role."

She Had To Alter Her Voice And Body As Well

There was also her accent that she needed to prepare for. She watched Sharron Stone in Basic Instinct and Nicole Kidman in To Die For. She also worked with a vocal coach four hours a day, with whom she read aloud high society magazines like Town & Country and the New Yorker.

She had to completely alter her body for Amy as well, gaining and losing 13 pounds three times, to play her at separate points in her life. While eating garbage, she was also practicing with a trainer four hours a day as well.

"I was eating crap, eating well, eating crap, eating well," she said. "Bulking up and leaning out." In the end, it all paid off and she earned her first Academy Award nomination. It was the role of a lifetime.

Now Pike is revisiting those badass qualities of Amy for her newest role in Netflix's I Care A Lot, where she plays a con-woman. Pike will never forget Amy though, she'll be a part of her for the rest of her life. We don't know whether that's a good or bad thing.

Next: The Truth About How Ben Affleck Cast 'The Town'