I'm listening to the Scrubs re-watch podcast, Fake Doctors Real Friends, in which they've been talking a lot lately about their secondary characters. Bill Lawrence, the show's creator, called some of these characters his "assassins". They would do "drive by comedy" - walking through a scene and dropping a one-liner that just absolutely killed.
I'm also recording my own writing advice podcast with my friend, Darci Cole, and we're focusing on How I Met Your Mother. This week, we're recording an episode that puts secondary characters first. Lily and Barney are not the main point-of-view character, but they are the only ones with storylines this week. The other characters are sidelined, including Ted, the main point-of-view character.
On the Scrubs podcast, Neil Flynn (the janitor, who also spent nine seasons as a secondary character on The Middle) pointed out that any long-running story is made on the backs of its secondary characters.
A strong main character is important to any story, but if you want your story to last beyond the first installment, you need a strong cast of supporting characters. How I Met Your Mother lasted for nine seasons (probably should have been eight), same for Scrubs.
Think of any long-running show: Cheers, The Office, The Simpsons, Law and Order, Grey's Anatomy, Supernatural, Big Bang Theory. No matter the genre, these shows all lean on their secondary characters to make the show feel constantly fresh.
Yes, they have good writers and a unique-enough setting. But if you list your favorite characters on those shows, it's probably not the main character.
Friends is one of my favorite shows, and they famously didn't have a "main character" - all six actors had equal screen time and equal pay. But that was at the end: the show was conceived of as Monica's show. Courtney Cox was the biggest star when the show started, and she was the glue that held the group together (her brother, her friend, her high school colleague, her neighbors, her hangout spot). As the six characters became equals, secondary characters were bumped up: Gunther, Estelle, the Gellers' parents, Mike Hannigan, and other love interests.
This got me thinking about my favorite book series, and it holds true here, too. Harry isn't the most interesting character in his world; Ginny is my favorite. Bella certainly isn't the most interesting character in her world; Alice is my favorite (unless it's the "movies" - and then Charlie and Jessica are the bright spots). Sarah Maas writes epic fantasy with badass females at the center, but the friends are always the more entertaining part of the books.
Some things I'm learning about secondary characters during all this:
They don't need to be fully fleshed-out up front. They can grow into who they're going to be, so leave it vague early on, giving yourself room to mold them into the places they're needed
Give them some of the best parts. Scrubs gave the best jokes to the backup characters, HIMYM gave secondary characters the spotlight all the time, Sarah J Maas has her secondary characters balance out the main character's shortcomings.
Start small. Populate the world with "sword carriers" or "extras", and bring them up to the forefront as needed. Gunther on Friends started as an extra and got promoted when the writers needed him to deliver a single-word punchline. He became more prominent as time went on, but he originally was hired because he was a capable barista and would lend credibility to their background scenes.
When you need to bring them to the forefront, spend some time writing up a little backstory to make them behave in a consistent way, and add to it as needed. Keep track of this backstory so you don't contradict yourself.