Kabumpo in Oz [Wizard of Oz #16]

During Prince Pompadore of Pumperdink's birthday celebration a magic scroll is found inside his birthday cake. It warns him that if he doesn't wed a "proper princess" within seven days, his entire kingdom will disappear. The prince, along with the old, wise elephant Kabumpo, the Elegant Elephant, set off on an adventure to the Emerald City to wed Ozma, princess of Oz.

Ruth Plumly Thompson (1891-1976) was an American author of children's stories.  Thompson was already an established children's writer when she was approached to continue the Wizard of Oz series following L. Frank Baum's death in 1919.  Between 1921 and 1939, Thompson published a new Oz book yearly.  After a more than thirty-year lapse, she published two new Oz stories in the 1970s, just prior to her death.