When Lucille tries to disguise Fracoeur's head with several hats and wigs in her dressing room, the one that looks like a Dracula hairdo resembles the hair style that -M- or Matthieu Chedid -the voice and singer for Francoeur- uses in his real on-stage persona.
Francoeur's black coat, hat and red scarf are based on the iconic Ambassadeurs Poster by Parisienne artist Henri de Toulouse-Lautrec
In this movie, a young singer is caught between the affections of a man named Raoul - who was a childhood friend of hers - and a mysterious figure who is shunned by society. This is nearly identical to the love triangle in "The Phantom of the Opera" by Gaston Leroux. In Leroux's novel, the singer's name is Christine rather than Lucille, and the mysterious figure is named Erik rather than Francoeur (and he is a disfigured man, not an enormous flea), but the other man (the childhood friend) is named is Raoul in both cases. Both stories also feature a character named Carlotta, though the two Carlottas are not connected in terms of plot.