The song "The Jitterbug", cut from The Wizard of Oz, is fairly well-known for a cut song whose original footage is lost; the audio of the song is included on the DVD along with home-movie footage of the filming, and it turns up in the stage version of the movie.
The thing I like about the song is that the first three notes of the refrain are the same as the first three notes of a song that would become a big hit ten years later: "Bali Ha'i" from South Pacific. Sing the first three notes of "The Jitterbug": it's the big three-note motif that runs through not only that one song in South Pacific, but the overture as well.
But to find the real origins of that three-note motif, you have to go back even before The Wizard of Oz, to the movie The Bride of Frankenstein, where Franz Waxman's music for the creation of the female monster is based around, yes, that same three-note motif: Da-da-DA... Ba-li-HA'I...
I'm not really sure why a somewhat exotic-sounding motif seems to be almost as ubiquitous as "How Dry I Am," and to have been used by three distinguished composers (Waxman, Arlen, Rodgers). But there we are.