While Rooney Mara plays a heavily inked and pierced-all-over computer hacker in “The Girl with the Dragon Tattoo,” in real life the actress hadn’t even had her ears pierced when she signed on for the role of Lisbeth Salander.

Still, she tells Allure magazine that getting her nipples pierced felt like the right move to fully inhabit the character.

“I’m naked quite a lot in the movie, and I thought, she has it in the book, and she should have it [in the movie],” Mara explains. “Because of all the tattoos and the makeup and the piercings, and the physical transformations my body has to go through, it would always feel sort of like I was in costume, even if I was naked. It just felt like a good [piercing] to get — a necessary one to get.”

Mara also got her lip, brow and nose pierced in addition to numerous holes in her ear, she revealed at last night’s London premiere of the David Fincher film. She says that, bizarrely, the ears were the most painful.

“I didn’t even have pierced ears. They put four holes in each ear, and, weirdly, that hurt the most,” Mara told the Daily Mail. “It was all very organized. With David, everything is measured and carefully considered. He wants what he sees in his head.”

At the premiere, Mara managed to walk the line between frilly and punk-rock in a long, white Givenchy by Riccardo Tisci dress that featured lace arms and daring cut-outs. She wore her dark hair pulled back in a bun, showing off the extreme line of her blunt-cut bangs.

DANIEL CRAIG THINKS ROONEY MARA IS ‘PHYSICALLY PERFECT’

Mara’s co-star Daniel Craig previously shared that it was this chameleon quality that made Mara such a perfect choice for the role.

“There were shenanigans going on while she was being cast,” Craig said. “David Fincher was adamant [about Mara] and I get that. Just look at the beginning of ‘The Social Network,’ she’s phenomenal. She’s got something about her, but also she’s physically perfect. When she puts the hoodie on and the leather jacket, she looks like a 14-year-old boy, she looks sexless. Which is perfect. The other side of it is that when she doesn’t have that on, she’s really sexy. That combination is absolutely true to the book.”

“The Girl with the Dragon Tattoo” opens in theaters on Dec. 21. It is the first in a trilogy of films based on Stieg Larsson’s books, the Millennium series.