So, Dr. Pipt knew how to make a powder that could bring things to life. But if he knew it could do that, he must have used it before, right?
Indeed. It seems he would have had more than one test subject, but the only one we meet is Bungle, the Glass Cat.
Bungle began as a glass ornament shaped like a cat. It featured emerald green eyes, a ruby heart, a spun glass tail, and tiny pink balls in its head for brains. When it was brought to life, the cat adopted a female gender.
The Glass Cat was tasked with catching mice, but she refused to as they would be clearly visible inside her body. Thus, as she wouldn't serve the purpose that she was brought to life for, she was considered a "Bungle," thus her name.
Bungle wasn't an entirely useless creature and would provide company for Margolotte as Dr. Pipt worked. As she did not need to be fed or cleaned up after, she made an ideal pet.
However, Bungle was also a cat and acted as such. Her decision to come when called was entirely voluntary and she often enjoyed going out on her own. Being able to speak, she would express her opinions, her vanity, and her believed superiority, particularly over her pink brains, which would move, leading her to point out, "You can see them work!"
When Dr. Pipt had to send Ojo to the Emerald City, he sent Bungle along with them, thinking that he might be rid of Bungle. Aside from her snarky commentary, Bungle adds little to Ojo's team and is left behind once Ojo reaches the Emerald City. The Wizard changes her pink brains out with clear ones to reduce her vanity, but by her next book appearance, they were pink again.
Perhaps her feline shape mixed with the Powder of Life helped Bungle not break so easily, because she soon began exploring Oz independently, her small size and transparency likely helping her observe without being seen. In this way, she learns many things about the Land of Oz, and it is this exploration that leads to her second Baum role in The Magic of Oz, in which she tells Trot and Cap'n Bill about the Magic Flower and leads them to it. She winds up having to rescue them as well by having to find the Wizard for help. But then, the Wizard needs some help himself when she finds him, which she's able to.
The Glass Cat didn't reappear in the Famous Forty Oz books. Typically, I avoid mentioning other works, but she is the main character of the story "The Ruby Heart" in Oz-Story 5 by Michael O. Riley which finally addresses what would happen if Bungle broke. It's also a very good character piece for her. She also makes a notable appearance in Eric Shanower's The Blue Witch of Oz. Finally, Gina Wickwar's The Hidden Prince of Oz reveals where the Glass Cat was actually made.
Like Eureka, Bungle is once again a feline character based on the way cat owners interpret their cat's personality. Bungle is vain and haughty and has a very high opinion of herself. The fact that she is also an animated glass ornament only ties in with her vanity. Bungle's vanity makes her a little difficult for other characters to work with, but she is not condemned for her attitude: this is simply who she is.