Mrs. Yoop is a wicked giantess and sorceress in The Tin Woodman of Oz. When she meets the Tin Woodman and his companions, she changes them into animal forms. She transforms Polychrome into a canary, the Tin Woodman into a tin owl, the Scarecrow into a stuffed brown bear, and Woot the Wanderer into a green monkey. She is the estranged wife of the imprisoned Mr. Yoop from The Patchwork Girl of Oz, who has been imprisoned for eating people. Unlike him, Mrs. Yoop transforms rodents into biscuits for her consumption. The Green Monkey Spell proves irreversible and has to be transferred to somebody else; in this case Mrs. Yoop who becomes, and must now stay, a green monkey. She is a Yookoohoo — a special kind of witch, "an Artist of Transformations" whose enchantments are extremely powerful. The other Yookoohoo in the Oz books is Red Reera in Glinda of Oz.
The Tin Woodman of Oz is a rarity in Baum's Oz canon, in that the author's manuscript of the book exists, and reveals the changes that Baum made for the printed version. Baum revised his original to make Mrs. Yoop more sinister; and he originally called Mrs. Yoop a "Whisp" (an otherwise unknown term in the universe of Oz) rather than a Yookoohoo.
Read more about this topic: List Of Oz Characters