The Australian actress, 33, appears alongside British actress Emma Mackey, 27, in the upcoming film after the pair have often been told they look alike.
Robbie has often spoken about how fans regularly mistake that she was in Netflix series Sex Education which actually starred Mackey.
Opening up in a recent interview, she explained how she and director Greta Gerwig wanted Mackey to star in the film so they could make a lookalike joke.
Things didn’t quite go to plan however once all of the actors had their full hair and makeup on.
Speaking to Buzzfeed, the Oscar-winner was asked: “Margot, what was it like to finally work with your doppelganger, Emma Mackey?”
She explained: “[Mackey] plays one of the Barbies in the movie pretty much because Greta and I thought it would be funny. We were gonna do this whole joke about us looking similar.”
“But once we got all dressed up as our Barbies, we were kind of like, ‘We don’t actually look that similar’. Like, when she’s got her brown hair and I’ve got my blonde hair, we don’t look that similar, so we didn’t put that joke in the movie.”
She also shared her typical response to when fans compare her to the British actress, saying: “When people come up and say, ‘I loved you in Sex Education,’ I just say, ‘Thank you so much.’”
Barbie, the highly anticipated film based on the iconic Matel doll, gets its London premiere tonight with a number of the star-studded cast including Robbie and Ryan Gosling due to attend.