In a Twitter Q&A with Glamour, the 25-year-old American actress revealed she was a big fan of the "comfortable" HANRO underwear she wore to play Anastasia Steele.
"I stole lots of the underwear," Johnson said. "They were comfortable."
Free pants? Just a perk of the job, along with her other Fifty Shades souvenir...
"I do have a flogger in my house," she added. "It's in the garage with dust."
Dakota, who stars on the cover of Glamour's March issue, was also asked to describe her co-star Jamie Dornan in three words - "sweet, goofy and charismatic" - and if she felt awkward when she met his wife, Amelia.
"No, she's incredible. Beautiful, glorious woman," she said. And Dornan was ever the gentleman on set, too.
"Jamie would be the first one to throw a blanket over me," she revealed. "And he did a lot of studying, just to make sure that I was as safe as possible. But there were some painful moments."
Like being tied to a bed?
Still, it sounds like Jamie Dornan is as dreamy as he looks. It's no wonder so many fans have already watched him play Christian Grey. (The film debuted at the box office over Valentine's Day weekend making a grand global total of £161 million).
Can't get enough of Fifty Shades? Don't miss this clip and see more of Jamie in his style file below...