And so recently she encountered a problem: 2012 is the Year of the Dragon, but she had already written about a dragon. So Brennan decided on another iconic Chinese animal.
The newly released Tale of Pin Yin Panda was inspired by Edinburgh Zoo's celebrated panda couple Tian Tian and Yang Guang, who arrived in Scotland last December.
"I called up Edinburgh Zoo to tell them about the idea of Pin Yin the panda and they loved it," says Brennan, who had her book's official launch at the zoo, where she got the chance to meet one of the giant pandas. "Tian Tian was gorgeous, chewing away on bamboo and smaller than I expected," she says.
The story's Pin Yin lives in the misty forests of Sichuan. She decides that 2012 should be the Year of the Panda. In a blurb, Susan Ramsay, Young Post's editor, called the book "a delightful read".
"I also wanted Chris Patten [former Hong Kong governor] to write me a blurb," says Brennan, who lives in Hong Kong. "So I looked up his contact on the internet and e-mailed him with a request for a blurb. To my surprise, he agreed."
Lord Patten described the book as "terrific" and promised to read it to his eight grandchildren.
Brennan thinks it was the Hong Kong connection that made it happen. "Lord Pattern told me he loved Hong Kong and his time in Hong Kong was the happiest in his life," she says.
Brennan says she loves making children laugh and telling them stories. She will be a featured author at the Young Readers Festival in March. "In my books, I write in rhyme, kind of like Dr Seuss. I use many words that are considered 'big words' for primary school students, but they have no problem understanding the stories," she notes. "They like absorbing knowledge".
Brennan grew up Australia, and moved with her family to Hong Kong in 1998. "I learned a lot about Chinese culture as I worked on my books and became fascinated with it," she says.
She is also puzzled by some things. In the Vietnamese zodiac, which is based on the Chinese one, the cat replaces the rabbit. "I wish someone who knows would tell me why that is," she sighs.
In return, she will tell you whether Pin Yin succeeds in getting a zodiac sign of her own.