Comment: Some other possible takeoffs based on Wizard of Oz trivia

The shoes in the original book were also silver, not ruby.

A possible take off of the shoes might be based on Baum's third book, the Scarecrow of Oz, where Baum wrote " “Then mebbe they're - they're - What do you call 'em, Cap'n Bill? Something 'bout the Pilgrim's Progress, you know." "Bunions," said Cap'n Bill. "Oh, yes; mebbe you've got bunions" (The Scarecrow of Oz, Chapter 3).

Since bunions are what you get on the soles of your feet (and Dorothy seems to represent the soul like the tinman, scarecrow, etc) represent something, maybe there is something here for what the shoes are (and why the color change from silver to ruby). Possible takeoff line - "Well blimey, That's a shoe of a different color, that is".

The Wizard of Oz book and movie themselves have several things that seem to be taken from Pilgrim's Progress - there is a witch in Pilgrim's Progress too - but she is Madam Bubble (sortof like Glinda appearing in a bubble in the movie), and there is an enchanted ground right before you get to the celestial city (instead of emerald city) that Madam Bubble is in charge of.