The on-screen singer of "La complainte de la Butte" is not Cora Vaucaire (credited in the titles) as she was deemed not good-looking enough to appear on film, so Italian actress Anna Amendola was put in front of the camera and mimed to the song...
The duo 'Nini' and 'Casimir le Serpentin' are based upon the real Moulin Rouge artistes La Goulue and Valentin the Boneless, both immortalised in the works of Henri de Toulouse Lautrec.
Eugénie Buffet (1866-1934) and Yvette Guilbert (1865-1944) were both popular 'Belle Epoque' singers, here played by their equivalents in 1950s French music.
This film has a 100% rating on Rotten Tomatoes.