Seth Ezekiel Cohen is a fictional character on the Fox television series The O.C., portrayed by Adam Brody. Seth is one of the "core four" characters on The O.C. alongside Ryan Atwood, Marissa Cooper, and Summer Roberts. Seth's friendship with Ryan, who eventually became his adoptive brother, formed a focal point of the series along with their romances. Seth married Summer in the series finale. His other relationships were with Anna Stern and Alex Kelly. Seth's goal was to attend Brown University, but he ends up going to Rhode Island School of Design (RISD) and continuing work on his comic book Atomic County. The role saw Brody win four Teen Choice Awards from five nominations, from 2004 to 2006.

Marissa Cooper is a fictional character on the FOX television series The O.C., portrayed by Mischa Barton. Marissa was among the original "core four" characters on The O.C. She is a privileged California native born into a wealthy family, residing next to the Cohen family's house. Throughout The O.C.'s storyline, Marissa is introduced to new characters who influence her perspective on life and her personality.