L. Frank Baum

Lyman Frank Baum was the author of The Wonderful Wizard of Oz. According to K9 Mark V's databanks, Baum was born in 1856. He was an actor at first, but became a successful writer with the Land of Oz series, for which he wrote fourteen books and several stage plays. Baum planned to build an Oz theme park on an island near California, but the plan never came to fruition.

Sometime after he had written the first Oz book but not yet the second, told Baum she would create the theme park and installed him as the Wizard of Oz in the Emerald City. Unbeknownst to Baum, she had actually made him the Master of the Land, creating a realm based on Oz in the Land of Fiction. This affected the timeline so that the Oz series never existed, aside from a single copy in the Doctor's TARDIS. Missy's plan was to draw the Doctor to the Land of Fiction and drain them brains, heart and courage to make them a husk of their former self. Although she had expected the Twelfth Doctor, she actually brought the Thirteenth Doctor who had taken Yaz, Graham and Ryan to see the premiere of the film adaptation of The Wizard of Oz, alongside a passing teenager named "Theodore".

Once the Doctor and her friends reached the Emerald City, she discovered the "Wizard of Oz" was actually Baum, who had been connected to the Master Brain. The Doctor forced Missy to disconnect Baum; however, without him to remain in place as the Master of the Land, Oz began to collapse as characters from other works of fiction invaded. To save it, Theodore assumed the title and was able to become her true self, taking the name Dorothy. The Doctor returned Baum to his home time. She told him he wouldn't remember the experience, like a fading dream, although Yaz believed it influenced the ending of the second book, The Marvelous Land of Oz. (PROSE: The Wonderful Doctor of Oz)

Other references
The Seventh Doctor once had an argument with "Frank L. Baum" about flying monkeys. (AUDIO: A Thousand Tiny Wings)

Behind the scenes

 * Baum was referred to "Frank L. Baum" instead of "L. Frank Baum" in A Thousand Tiny Wings, likely as a mistake.
 * In The Wonderful Doctor of Oz brought Baum to the Land of Fiction after he wrote The Wonderful Wizard of Oz but not having yet written The Marvelous Land of Oz, the latter of which in the real world was published in 1904. Baum did not actually announce the idea of an Oz theme park until 1905, and abandoned it shortly thereafter.