For Bella Heathcote, taking on the role of Fifty Shades Darker’s villain, Leila Williams, was a total thrill—especially when it came to her wardrobe. Known for her classic-meets-glam fashion choices off-camera, the 29-year-old Australian actress found herself in uncharted territory when tapping into the aesthetic of her troubled character, who begins stalking Anastasia Steele (played by Dakota Johnson)—the new lover of her ex, Christian Grey (Jamie Dornan)— after suffering a mental breakdown. But the fact that Heathcote had a hard time relating to her character’s fashion choices is probably a good thing.

“In the past, my roles have definitely influenced my real-life style—until Leila,” Heathcote recently told InStyle. “She dresses pretty crazy.” While Heathcote’s style may not be anything like her character’s, the star’s costumes played a key role in helping her to channel Lelia’s inner turmoil. “We basically put something that looked like it could be a nightgown over jeans and boots, and I was immediately in the character,” said Heathcote, who also dyed her blonde locks a dark brown shade for the film. “I was just completely undone, which was great.”

Getting Leila’s outward appearance just right was pivotal in conveying her current frame of mind. “She's so unstable,” said Heathcote. “It's such a specific choice—or lack of choice—when it comes to what she's wearing, and that completely indicates her mental state. That was actually really helpful for me in playing her.”

Luckily for Heathcote, there were plenty of behind-the-scenes laughs that balanced out the dark mindset of her character during filming. And her favorite moment from the set is one that any Fifty Shades fan can appreciate. “We were shooting on location at an apartment, and Jamie got inside this strange looking thing that, to this day, I still have no idea what it even was,” said Heathcote. “I guess it was a little one-man sauna bed or something, but he got in there and was clowning around. And he just had me in stitches. I seriously almost wet my pants. I assume it was some sort of sweat box that he was in, but I really don’t know. It was pretty weird looking, so I took a photo and posted it on Instagram.” See the snap below, and catch Heathcote in action in Fifty Shades Darker, now in theaters.