In the Land of Oz, X is a rare letter that is almost never heard. One exception is from Ojo in Oz, which is the twenty-seventh book in the Oz book series, and the thirteenth Oz book written by Ruth Plumly Thompson.
The Oz Wikia describes X. Pando as follows:
"X. Pando the elevator man provides lifts to the top of Moojer Mountain in the Munchkin Country of Oz.
He is a tall, serious-looking fellow in a blue leather uniform; he emerges from a stone doorway set into the surface of the mountain. His legs expand accordion-like, allowing him to reach atmospheric heights, high above the top of the mountain itself. His lifting is controlled by the gold buttons on the front of his jacket. He demands payment for his service — though that payment can be as minor as dancing a waltz. (Ojo in Oz)
Without going into detail, X. Pando claims to derive his unusual abilities from his father. In this, he resembles Kuma Party, another magical anomaly of Oz who gained his special skill from his paternal parent."
John R. Neill continues on as illustrator and provides a single piece of art depicting the only character in Oz I could find that starts with an X.
Here he be, dancing with Snufferbux, a brown bear... with a belt?
James C. Wallace II
Royal Liaison of Oz