If you are only familiar with the story of The Wizard of Oz from the 1939 film, it's well worth your time to track down a copy of the book (titled The Wonderful Wizard of Oz, published in May of 1900).
There are a number of differences between the book and the film, mostly involving a great deal of the material from the book not making it to the screen*
*Which is fair enough, that's what film adaptations of books are supposed to do.
For starters, the slippers are silver*, not Ruby Red (The movie was in technicolor, so they changed it to take advantage of the technology).
*For those who enjoy literary metaphor - they represented the silver standard, the yellow brick road represented the gold standard. The emerald city to which they were traveling represented cash currency and in the book is revealed to be a fake (they made all the visitors wear green colored glasses). L. Frank Baum - neither subtle with a metaphor nor a huge fan of turn of the century economic theory.
Another change from the book is that the Munchkins were just one of the four quadrants of Oz. (The others being the Winkies, the Quadlings, and Gillikins, in case you were interested.) We get to meet the Munchkins, Winkies and Quadlings. The impression is that the Gillikins can go screw themselves. They live in the North - which is also where Glinda the supposedly 'good' witch hangs out. Perhaps she had them too busy making counterfeit wallets for export to participate in the story. Who can say.
The important point here is that when we DO get to meet the Quadlings, they live in a magnificent underground city. Dorothy asks them how there is light to see, and is told that the Quadlings have discovered a wonderful material called 'Radium' that gives off a glow, so they've coated every single inch of their city with it.
Which means that in about 10-15 years ALL of the Quadlings are going to die a horrible death from an exciting variety of cancers.
Somehow they avoid mentioning that in the movie...
Afternote - I was somewhat disappointed to realize earlier that I had misremembered this, and that it was the Quadlings who used the radium and not in fact the Winkies.
This has disappointingly prevented me from being able to work the phrase 'Dramatic rise in the incidence of Winkie Cancer' into the discussion.
For that I am truly sorry.