In between Le groom vert-de-gris (“The field-gray bellhop”) and their new adventure, Le fétiche des Marolles (“The Marolles Fetish”), Schwartz and Yann made a one-pager set in the same universe, a prequel to both stories. It was published in the 75th anniversary issue of the Journal de Spirou (#3914), but this might be a more suitable occasion for it. Readers should be warned that it is pretty gruesome.
The zazous were a kind of wartime hippies, big into jazz and extravagant fashion. The French title for this story, Tombe la neige (“Fall, snow!”), is probably taken from this beautiful but rather depressing Belgian winter song.