The Half of It is partially based on Cyrano de Bergerac — and whether you read the play or saw the Wishbone episode you know the basic story: A handsome suitor (Christian) asks a witty outcast (Cyrano) to write love letters for the woman (Roxanne) that they both happen to be in love with. Roxanne falls in love with Christian without realizing that his words belong to Cyrano.
But Wu's adaptation has an LGBT update: The "outcast" hired by the popular Paul to help him win over Aster is a girl named Ellie, who also likes Aster. In the official press materials for the film, Wu talks about how the film is also based on intimate friendship she had as a teenager, so it was important to get the dynamics right in the cast.
Since this is set in high school, as all the best angsty modern day literary adaptations should be, the cast of The Half of It is filled out with the teachers and parents of these kids. Here's everyone you see in the film and where you may have seen them before.