In the movie version, Seth has one of the biggest character changes. In the book, he is a quiet, mysterious, cool boy who has just transferred from Austin. He is described as having dark hair and olive skin, and his father’s name is Alejandro, so all signs indicate Latinx coding. His parents are artists and he is not used to small town schools. His stance on a more liberal city reinforces Viv’s feelings that her school is particularly backward.
The movie version of Seth is completely cheerful, sweeter and the boy next door. After the summer holidays he’s taller, he has cooler hair and Nico Hiraga absolutely nails Seth’s new awkward cute skater personality. Changing Seth to an East Rockport local streamline his interaction with Viv. One thing is for sure, in both versions Viv was completely beaten with him.