I have found a...curiosity.
Classic live-action Disney fans will certainly remember 1948's So Dear to My Heart, the story of a country lad and his mischievous pet lamb, starring Bobby Driscoll and veterans Beulah Bondi as Granny and Burl Ives as Hiram. (This is the film where Ives sings one of his big hits, the Oscar nominated "Lavender Blue.") The source material for this has always been noted as the Sterling North book Midnight and Jeremiah.
Somewhere in my early teens (and I can date that by the price on the paperback book, which was 95 cents), I found a copy of the book version of So Dear to My Heart, with a copyright date of 1947. I figured when the book was reprinted, the name of the book was changed to that of the movie, and the name of the lamb from Midnight to Danny, just as the publishers of Rose Wilder Lane's Let the Hurricane Roar! changed its name to Young Pioneers after the television movie it was based on, and changed the names of the protagonists from "Charles and Caroline" to "David and Molly" to avoid conflicts with the Little House on the Prairie television series.
Well, I have come upon a copy of the original Midnight and Jeremiah in a used bookstore, copyright 1943. To my surprise, it is more of a children's book than what I though the "original" was, with pictures on every page by famed illustrator Kurt Wiese. The characters and the basic story are all familiar, but at the same time markedly different, and although I haven't read it yet, it looks like the story ends at Christmas.
It almost looks like North either rewrote the book for adults previous to the film's release, or based the rewritten book on the screenplay for the Disney film. It would be interesting to know the story behind the two volumes.
(Later: The book From Walt To Woodstock: How Walt Disney Created The Counterculture states that the Dan Patch sequence was added to the film by Walt, who, like Jerry, got to meet the famous trotting horse Dan Patch when the horse's train was stopped in Marceline, MO, where Walt spent the happiest days of his childhood. So the renaming of the lamb and the sequence was Disney's, not North's, lending further credence to the book being a novelization of the film.)
Cover picture link)