https://en.m.wikipedia.org/wiki/The_Scarecrow_of_Oz

https://en.m.wikipedia.org/wiki/The_Royal_Book_of_Oz

Scarecrow discovers that, in a previous incarnation, he was human. More specifically, he was the Emperor of the Silver Islands, a kingdom located deep underground beneath the Munchkin region of Oz, inhabited by people who resemble Chinamen.