Lili Reinhart’s Hair Transformation for

23.09.2026, 15:28 allure.com

Fans of Ali Hazelwood’s The Love Hypothesis expect a few things from the book’s film adaptation: fake dating, SPF (handfuls of it), and a deeply upsetting conflict. Some might even be waiting for a nod to the Star Wars fanfiction that inspired the novel. What we didn’t see coming (until last July) was a brunette Lili Reinhart playing the story’s protagonist Olive Smith. The reception to her casting was positive, and much of it was focused on her hair. After all, Reinhart had been on our screens as golden-blonde Betty Cooper on Riverdale for six years.

Frédéric Bélanger, hair department head for the film, understood the expectations that come with bringing a best-selling romance novel to life. “Everybody has a picture in their head,” he says of the characters’ physical appearances—and turning Reinhart into Olive goes beyond putting her in a lab coat and closed-toe shoes.

Ahead, Bélanger details Reinhart’s transformation, how hair furthers the stories of both her character and costar Tom Bateman’s, and gives us a glimpse of the happenings behind the scenes.

“Everybody wanted to turn Lili into a brunette,” says Bélanger, but Reinhart didn’t dye her hair for the film. What you’re seeing onscreen are two wigs created by Bélanger and wigmaker Stacey Butterworth.

Landing on the right hair color for the actor and her character took multiple tries: “We had to choose a level of brunette that wasn’t so dark that it looked shocking,” Bélanger says. The process started with a mood board that kept readers’ expectations for the character in mind. “On the cover of the book, it’s like a red- [or] warm brown,” he says. The team tried that exact hue as well as honey and chestnut browns and ultimately landed “somewhere that sits between dark blonde and light brown.” (At Allure, we’re partial to calling it by the portmanteau, bronde.) After deciding on the shade, they began constructing the wigs. Butterworth created a mold of Reinhart’s head before installing the hair, strand by strand, into the base.

Once you know someone’s wearing a wig, your eyes start looking for it, right? Bélanger says that this posed some real challenges. “We had to think about the hairline, the density—all the details that will make a difference,” he says. “Sometimes it can look wig-y. I think everybody was so concerned from the get-go with that.” ​

To ensure the wigs looked as realistic as possible on camera, Bélanger and Butterworth added different-colored strands for dimension after seeing it on Reinhart. They also added lighter-weight, fluffy strands throughout the wigs that caught the air easily, so they behaved the way natural hair would outside in heat and humidity—and on a girl watching her (ripped) fake boyfriend play ultimate Frisbee.

Hiding Reinhart’s naturally thick hair under the wigs required multiple steps and lots of pulling. “I had to really work it precisely so that it disappeared,” says Bélanger, a process that required him to pull Reinhart’s hair “very, very, very tight,” but “not in a way that would hurt her.”

It would, however, sometimes tug on the perimeter of her face. “She would be like, ‘Fred, you're giving me a facelift. People will think I have a facelift,’” he says, laughing. Ultimately, he loosened it. “She was really mindful of me not doing that.” Once the wig was secured in place with U-shaped pins, Bélanger made sure to blend the part with Kryolan Dermacolor Camouflage Creme, which was color-matched to Reinhart’s scalp.

Styling the hair for this film could easily have been an afterthought. Olive is a STEM student who spends a ton of time at the library, but Bélanger was meticulous in capturing the character’s lifestyle. “Olive is not the perfect girl,” he says. “She’s a student. Students are overwhelmed. We wanted the hair to look like it could be lived in.”

You’ll notice that when Olive is watching Love Island on the couch with her best friend Anne, her hair looks freshly washed and unstyled. “You're in pajamas with your best friend eating popcorn and chocolate,” says Bélanger, who adds that in that moment between confidantes, “nobody cares.” “We worked the hair in a way that it would intentionally look like she did it herself.”

You’ll also notice that when she is dressed up to go to a party, her hair is styled, but not over-the-top or overly glamorous. “She wears a beautiful red dress,” he says, painting a picture of how Olive might have gotten the look in the story. “Maybe she didn't go to the hairdresser because she's a student. Maybe Anne did it for her.” Everything is done with precision, as if it were done by a scientist in a laboratory.

Bateman, who plays Dr. Adam Carlsen, also goes through his own grooming journey. As “Dr. Evil” (a nickname given to him by his students) softens, so does his grooming. “At the beginning, his hair was a bit stiffer,” Bélanger says. “You really see the progression of him loosening up and being more willing to be warmer. The hair translated that.”

The lore is as follows: The Love Hypothesis was based on a fanfiction about Star Wars characters Kylo Ren and Rey, who are played by actors Adam Driver and Daisy Ridley. Did that impact the film? Naturally. “They created these characters thinking of these two other characters, so it had a repercussion in our decisions,” says Bélanger. One such decision had to do with Bateman. “The actual ‘Dr. Evil’ doesn't have a beard on the cover” (which has Driver’s likeness).

The thought process surrounding the decision was simple: “Is it going to be the best look for him?” says Bélanger. “You need to always question how he is going to feel being completely clean-shaven. Because you always want people to relate and to fall in love with him as well.”

Ridley is actually married to Bateman, which posed an opportunity: “I know that they tried to have Daisy play a little part in there just for fans,” says Bélanger. “For whatever reason it didn't work out.”

The scene illustrated on the cover of Hazelwood’s novel—Olive and Adam’s first kiss—is the catalyst for everything that happens in the story and was shot multiple times from different angles. Bélanger created a chignon with a silhouette similar to the cover art but woven like a bow, understanding it would be important to capture it as close to the source material as possible. After all, “the cover of the book is how you enter a story,” he says.

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