I've noticed that in books and movies, supporting characters are usually more interesting than their main character counterparts.
As evidence of this point, contrast the following attention-grabbing supporting characters to their less interesting lead character:
Luke Skywalker (Star Wars)
Any other Star Wars character
Captain Kirk (Star Trek)
Harry Potter (Harry Potter)
Ron or Hermione
Captain Hawkeye Pierce (Mash TV show)
Corporal Radar, Major Houlihan, or Corporal Klinger
J.B. Jeffries (Rear Window)
Thelma Ritter (nurse)
Maria (West Side Story)
Frodo (Lord of the Rings)
Simba (The Lion King)
Timon or Pumbaa
Marty (Back to the Future)
Going to the mall
Shopping malls in the United States are arranged in a way that is similar to fictional stories.
Shopping malls usually have one or more of what are called anchor stores (the main character). An anchor store is the muscle that draws the customer volume and sales. They do this by providing name recognition.
“Honey, I’m going to the mall, the one with Nordstrom.”
But they're not very interesting.
It's the myriad of smaller stores (sidekicks) that sell souvenirs, used video games, and women’s and household scented items, that gives malls their individual personality.
Which is more interesting: Dillard's or the stores that sell gourmet cookies, body lotions, and teenage jewelry?
So it is with sidekicks and other minor characters on the screen and on paper.
My relatives tend to visit us only when our children are in town. Clearly, my wife and I are less interesting than our kids.
Main characters are like the parents in a family, while sidekicks and minor character are the children. Parents don’t catch the eye as much as a baby in a stroller.
What do sidekicks and other minor characters provide?
Sidekicks provide increased depth and richness. What would Dickens’ A Christmas Carol be without Tiny Tim?
Just so you can be culturally literate, Charles Dickens had a difficult time coming up with the ending of A Christmas Carol until he got the idea to have Tiny Tim die in Scrooge’s vision of the future. This was the final straw that caused Scrooge to change from being bad to being good.
All the used facial tissues at Christmas time can be blamed on that poor, crippled minor character.
Sidekicks and minor characters provide:
Trust and loyalty
A humanizing view
Perspective, context, and contrast
Sidekicks and minor characters help to,
Propel the plot
Set the tone and reveal information
(sometimes) Provide the POV character
Sidekicks and minor characters must provide a surprise. This is a requirement. They must delight. What would Disney’s movie, Aladdin be without that scratchy-voiced parrot? What about Kramer in the Seinfeld TV show? They are more entertaining than their main character counterparts.
Besides providing a surprise, sidekicks and minor characters must possess an opposing trait. The parrot in Aladdin provides impatience and that fingernail-on-chalkboard voice. Ron Weasley in Harry Potter is whiny, while Hermoine Granger is conceited.
Not too 3D
A sidekick or minor character must not be too 2D or too 3D. Provocative is good. Stimulating is good. Somewhat fascinating is good. But never enough to overshadow the main character.
Sidekick and minor characters must have a distinct personality but not a strong, pressing goal. Ease off on their back stories. Big goals and entire live struggles are reserved for the main characters.
Sidekicks can be silly or serious, harmless or dangerous. But they must be something. They're the zing in the spaghetti sauce and the high heels in the prom outfit. They're perhaps even the icing on the cake.
And everyone likes birthday cake!