- "Eureka isn't purple or pink; she is white, or at least was," said Dorothy. "It's this queer light that gives her that color." "Where's my milk?" asked Eureka, looking up into Dorothy's face. "I'm most starved to death!" "Why Eureka!" cried Dorothy. "You can talk!" "Of course I can talk, funny isn't it?" Eureka replied..."
- ―Dorothy and the Wizard in Oz (1908)
Eureka is introduced in L. Frank Baum's fifth Oz book titled Dorothy and the Wizard in Oz, published in 1908. She is described as being a beautiful female kitten who was originally a stray. She was found by Dorothy Gale's Uncle Henry, that he gave to her telling her that the name means "I have found it!" She is Dorothy's pet, who carries her in a small cage on a train with her to San Francisco to visit her relatives on the Hugson farm. While riding with Bill Hugson's nephew, Zeb, a earthquake hits and opens a large chasm in the ground. Eureka falls in the Earth's bowels and straight into the ground in another dimension with Dorothy, Zeb, and his horse, Jim, into the Land of the Mangaboos. There, everything, even the people, is completely made of vegetables. Eureka is said to have all pure white fur but when the strange lights in the Mangaboo's magic carven make her appear to be pink and purple, she is stained permanently and from then on she appears to have pink and purple blotches on her.
Eureka traveled with Dorothy through the Valley of Voe, the Land of Naught, and the Den of the Dragonettes before eventually being taken with her to the Emerald City in the Land of Oz. A few days after they had arrived, one of the Wizard's Nine Tiny Piglets went missing. Since she had frequently asked permission to eat one of them, she became the prime suspect and was put on trial. The accusations were proven false however, when she revealed the location of the lost piglet, safe and sound. (Dorothy and the Wizard in Oz)
She later somehow became Pink, and became known as the Pink Kitten. (The Patchwork Girl of Oz)
- Dorothy and the Wizard in Oz (first appearance)
- The Patchwork Girl of Oz (mentioned)
- The Scarecrow of Oz
- The Magic of Oz
- The Wonder City of Oz (mentioned)
- In Eric Shanower's book 'the Magic Island of Oz, Eureka is a main character.
Eureka, as noted above, is a "white kitten" on her first appearance. By the time of The Patchwork Girl of Oz, though, she has become a pink kitten (Chapter 11). She is mentioned again in The Scarecrow of Oz as "Eureka the Pink Kitten" (Chapter 24). Dorothy has a "Pink Kitten" again in The Magic of Oz (Chapter 20), and a "purple kitten" in Glinda of Oz (Chapter 5); but Dorothy is not known to have had any pet kitten other than her. Several authors have offered explanations for the her color change.
How Eureka got to the Land of Oz is also a mystery. At the end of Dorothy and the Wizard in Oz, she was put on trial for eating one of the Nine Tiny Piglets. Finding herself in disgrace after the trial, she asks Dorothy to bring her back to Kansas (Chapter 20). When the Shaggy Man mentions her three books later (in The Patchwork Girl of Oz), there is no explanation for how she ended up back in Oz.
March Laumer's The Careless Kangaroo of Oz (1988) has Eureka left behind when Dorothy, Aunt Em, and Uncle Henry move to Oz; an adventure involving Polychrome, the Shaggy Man, the Wogglebug, and Sky Island leads to her color change to pink and her return to Oz. Laumer returned to Eureka in The China Dog of Oz (1990).