Analyzing character portrayals in picture books is a well-researched area in the humanities, not least in literature and gender studies. It fulfills an important function as these depictions can be seen as confirming or challenging hegemonic notions of gender and age. Specifically, this study concerns the picture book character Mamma Mu. She has been a subject of interest for academic studies before this one. However, there are no studies centered around her age and how this affects whether her actions can be considered intelligible or not. Placed in the intersection of gender, literature and girlhood studies, and from a skew theory perspective as presented mainly by Maria Margareta Österholm (2012), the aim of this thesis is to study how Mamma Mu as an adult feminine subject exhibits different age-related expressions of femininity, and how she relates to notions of accepted behavior in relation to adulthood. Based on the extremes of expected as well as adult and skewed as well as childish femininity, this thesis thus argues that Mamma Mu exhibits an oscillating movement between these extremes.