Lucy is part of the secondary main cast.

Lucy is one of Mabel's best friends ever since they were younger. While they're not opposites of each other, they definitely had their differences. Lucy was more of the golden retriever, she was always excited to learn something new, but knew when to get serious when there was a problem. Lucy also had a big heart for animals and spent a lot of time with them when she could.

To see her design you can look at her toyhouse!: https://toyhou.se/17212105.lucy