Being fairly new to gypsy jazz (only listening/playing for the last couple years), when I first heard Nuages, I assumed that I had heard it somewhere before, but not sure where or when. Up until about the year 2000, I was not even acquainted with Django Reinhardt.
But I just figured it out: the theme music to the Jackie Gleason Show, which I remember watching every week as a child, contains the same melody line, at least the first 7 notes. It's called Melancholy Serenade; check it out on youtube if you're not familiar or have forgotten it.
Anyone else notice the similarity?