The Emerald Enchantress of Oz, by Peter Schulenburg - This is a pretty interesting Oz story, featuring an enchantress who was put under an enchantment herself by her sisters, the Wicked Witches of the East and West. The diaries of the two witches play a major part in the story, as do Mrs. Yoop and Boq. The writing is a little awkward in spots, but the story is quite good.
A Promise Kept in Oz, by Dennis Anfuso - This was actually a graphic novel, and one done in a rather comical fashion, with a lot of meta-humor about how the pictures are all in black and white (which they are, except for the cover), and how much time the various characters get on stage. There's also sort of a sitcom setup in that Mrs. Yoop (still in green monkey form) has a roommate and an obnoxious neighbor. It's still a coherent and consistent Oz story, however, with Mrs. Yoop taking advantage of a favor that the Scarecrow owes the stork who rescued him back in Wizard.
Since both books do include Mrs. Yoop, it got me thinking about how to fit her history together. Obviously, when a fan writes a story about an Oz character, they don't always check to see what other fans have already written about that character. In fact, it can often be very difficult to do so. Still, as a self-professed continuity nerd, I like to try to work these things together as well as I possibly can, and there isn't anything all that contradictory in the accounts I've read of Mrs. Yoop. Emerald Enchantress, while published in 2003, actually takes place not long after the events of Tin Woodman; the Royal Timeline of Oz places the events of both in 1916. In Enchantress, the former giantess uses her magical jewelry to temporarily take forms other than that of a green monkey, transferring the simian form to Boq when she does so. Emmy the Enchantress takes away enough of her jewelry to make her powerless to do this anymore, but the yookoohoo receives no additional punishment, so her state really isn't changed by the events of the story. Promise Kept has Mrs. Yoop end up as an ordinary brown monkey, with a ring that prevents her from using any more magic. While this graphic novel refers to the events of Tin Woodman as having taken place over ninety years previously, I also have to take into account the late Fred Otto's short story "The Fate of the Yoops," which appeared in the 1983 Oziana. In this story, Reera the Red offers to help Mrs. Yoop but actually tricks her, and transfers her green monkey form to her husband Mr. Yoop, while turning Mrs. Yoop herself into a turtle. The former giantess is green at the beginning of the story, but I think it's easier to explain how her color changed than how she would have changed back from a turtle, so it's most likely that Promise Kept actually takes place BEFORE the Otto tale. The only other story I can think of that stars Mrs. Yoop is Time Travelers of Oz (not to be confused with Time Travelling in Oz or Time in Oz), which states that Mrs. Yoop and Reera are sisters. Yeah, I know the former is (or at least was) a giantess, but the story has it that she and her husband didn't take on the forms or habits of giants until after they were married. While this would make it odd that Reera doesn't recognize Mrs. Yoop as her sister in the Otto story, but I get the impression that they would have been estranged for some time by then.
Another interesting thing to note about "The Fate of the Yoops" is that Mrs. Yoop travels to retrieve her husband with a familiar of Reera's named Thrug, who is in the form of a donkey. In the 1985 Oziana, Otto has another story called "Mombi's Pink Polkadot Vest," in which the Wicked Witch of the West has a donkey named Thrug, who had originally been a dragon. I think it's likely that Otto meant us to assume that this was the same Thrug, who presumably went to live with Reera after the Witch died. In Red Reera the Yookoohoo and the Enchanted Easter Eggs of Oz, we learn that one of Reera's other familiars is an ant who prefers to remain in the form of a horse named Bone White.