Marli is the Swordfish Princess, with her crown being a cheerful swordfish hooked in her hair. Her depiction in the series differs between the books and animated series. In the books, Marli is a very intelligent girl, who can work without a lot of effort. However, asking her to read her work in class is not a good idea as Marli is very shy and lives with shame for reasons she doesn't know. In conversation, Marli listens much more than she talks; sometimes her friends think that she does not pay a lot of attention, but Marli is really waiting for everyone to finish talking before giving her own opinion, often covered with reason. In the cartoons, Marli is shown as an arrogant girl and a rival to Ester, wanting to overcome her at school and at any activity. However, she is a good girl despite all this.