Willa is Woody's younger sister, who only appears in the episode "My Sister's Keeper". She uses Woody's catchphrases "Hurtful!" and "Dang it!". Willa comes aboard the S.S. Tipton for her vacation, and Woody asks that Cody show her around. Though both brothers believe that anyone related to Woody would be repulsive and awful company, Willa's unexpected beauty leave Zack and Cody both instantly attracted. Cody asks her out, but after he says that they "shouldn't hold in their true selves" Willa reveals that she is, in fact, very similar to Woody, utterly disgusting Cody.
Bailey becomes jealous of Cody and Willa together, which makes her realize that she still likes Cody. Cody lies to Willa that he is still in love with Bailey, in a desperate attempt to let her down gently, making Bailey briefly happy, but still breaking Willa's heart.
At first, Willa seems beautiful, funny and sweet, but later on in the episode, it is learned that she is as bad-mannered and gross as Woody is.