The characters of Simon and Louise are approximately one year apart in age in the film, Simon is supposed to be 18, and Louise is supposed to be 16. But, in real life, the opposite is true, Gaspard Ulliel, who portrays Simon, is approximately one year younger than Mélanie Laurent, who portrays Louise.
Alysson Paradis's debut.
When Louise points out at a framed photo of Simon when he was younger, he says "that's my Jim Morrison look". Gaspard Ulliel and Jim Morrison are both buried in the Pére-Lachaise cemetery in Paris.