Miss Schmalzbrot and Billie Balloonist are sisters. Miss Schmalzbrot is the older sister, while Billie Balloonist is the younger one. The two are very different and often can't stand each other. Yet most of the time, they are inseparable. After all, it’s quite nice to have a sister and thus an ally against the strange ideas of adults. Together, they experience plenty of funny adventures that any sibling can relate to.