These characters do the heavy lifting of inserting literary references into the show and guiding us towards the theme.
It's great if, like Dawson (James Van Der Beek), Sam Weir (John Francis Daley), and Rory Gilmore (Alexis Bledel), they are the main character, but it isn't vital. Seth (Adam Brody) from The O.C. is second fiddle (well, at first), while Matt Saracen (Zach Gilford) and Julie Taylor (Aimee Teegarden) from Friday Night Lights are far from the spotlight in the pilot.
As long as they drop references to Moby Dick and wax poetic about their favorite filmmakers while the cool kids are busy partying, they'll fit in anywhere within the story.