Ryan Gosling said Margot Robbie would fine anyone on the 'Barbie' set who didn't follow her rule to wear pink once a week

• Margot Robbie had everyone on the "Barbie" set wear pink one day a week. 
• Ryan Gosling, who plays Ken in the film, said Robbie would fine anyone who didn't wear pink.
• Robbie then donated the money from her mandatory pink day to charity. 

From the set design to its stars' outfits on the red carpet, the "Barbie" movie has been completely dedicated to the color pink. 

And now it's been revealed there was a mandatory "pink day" that the cast and crew followed every week during filming. (Regina George would be so proud.)

Ryan Gosling told People that the weekly dress code was Margot Robbie's idea. 

"Margot had this pink day once a week, where everyone had to wear something pink," Gosling said. "And if you didn't, you were fined." 

"She would go around collecting the fines, and she would donate it to a charity," he added. 

Gosling said the male crew members loved "pink day" and even made a special gift to honor Robbie and director Greta Gerwig. 

"At the end of the film, they all got together and, with their own money, made pink crew shirts with rainbow fringe," Gosling said. "It was this opportunity for them to show their respect and admiration for what Margot and Greta were creating." 

"It was almost like that scene at the end of 'Dead Poets Society,' where they all get on their desks and say, 'O captain! My captain!'" he added. 

Simu Liu told People that Robbie even hosted a sleepover for all the actors who play Barbie in the film.  

"The Kens were allowed to either visit briefly or to phone in and say hi," he said. "So we made sure to show our support but not be overbearing with our presence." 

Gerwig told GQ that Gosling couldn't make it to the sleepover, so he sent over a Scottish man in a kilt to play the bagpipes and read a speech from the film "Braveheart."