Mercy Watson is a fictional character from a children's book series written by Kate DiCamillo. She is a lovable pig who lives with her owners, Mr. and Mrs. Watson, in a cozy house. Mercy enjoys adventures, especially when it comes to food, particularly her favorite treat: buttered toast. The series features Mercy's humorous escapades and her interactions with various characters in her neighborhood, including the Watsons' neighbors and the local animal control officer. Each story highlights themes of friendship, family, and the joy of simple pleasures, making it appealing to young readers.