Disney & Oz Part I: Why Walt's dreams of an Oz movie never came to be

The Mousketeers go to Oz?

As with so many things, Walt was a bit ahead of his time with his original idea of how to use the Oz property. His initial plan was to use the Oz books as episodes for his Disneyland TV show which later became The Wonderful World of Disney. He picked the aptly named Dorothy Cooper to write a two-part teleplay with a classic "Dorothy returns to Oz" story that would also bring in other book characters, loosely based on The Patchwork Girl of Oz. 

After seeing the script, Walt decided TV was too limiting and instead wanted an adaptation of The Rainbow Road to Oz as a full-length feature film. He still wanted the Mousketeers to play roles in the film with Annette Funicello as the Princess Ozma and Disney star Tommy Kirk as the revenge-bent son of the Wicked Witch. The project got pretty deep with concept drawings about showing ideas based more on the original book illustrations than the MGM movie. 

By late 1957, things were moving ahead as Walt bought the rights to Dorothy and the Wizard of Oz reportedly for as much as he'd paid for the previous 11 books. One episode of The Mickey Mouse Club opened with a long dance number of the Mousketeers in costume, which seemed to show how it could work. 

And it didn't.

By reports, watching that number made Walt realize that the movie just wasn't working. He was mindful of the budget as the horror stories of the 1939 production were still fresh and Disney was already handling the costs of Disneyland. There was how the script didn't seem to be clicking and the musical score by Tom Adair & Buddy Baker didn't come close to matching the beloved MGM movie's songs. 

Walt decided that if he couldn't do Oz right, he shouldn't do it at all and so, with little fanfare, Rainbow Road was canceled.