Adapted from a novel by Joyce Carol Oates, named "Lives of the Twins".
When Chloé's mom is talking to the doctor, she's wearing the golden cat head pendant that Louis gave Chloé for her birthday.
François Ozon had the project in mind since 2013, but at the time he didn't think of casting Marine Vacth, who he'd just directed in Young & Beautiful (2013), as she was too young. By the time filming actually started some three years later, Vacth had become a mother and matured, leading Ozon to see her in a new light.
When Chloé is leaving the museum, she crosses under a site specific artwork from Brazilian artist Henrique Oliveira. The artwork "Baitogogo" was created exclusively for this exhibition at the Palais de Tokyo using the building's original structure and was in the museum's building from 30/11/2013 to 18/12/2016. The museum where Chloé works is actually the famous Palais de Tokyo.
Louis says to Chloé that he and Paul are "mirror twins". The term mirror twin is used to describe a type of identical, or monozygotic, twin pairing in which the twins are matched as if they're looking into a mirror -- with defining characteristics like birthmarks, dominant hands, or other features on opposite sides. Mirror twins always come from a single fertilized egg and share the same genetic makeup. That said, the exact cause of the mirroring in some twin pairs is unclear. Some researchers suggest mirror twins occur when an egg splits later in the fertilization process. (Eggs usually split within a week of conception -- or less. However, some split later, around 7 to 10 days after -- and this may explain the variation. However, researchers have yet to determine why mirroring occurs.)