Supporting characters “support” the story, plot, theme, and most importantly, the protagonist – either with achieving his or her goal or obstructing the hero along his path.
Here are three steps to help you create effective supporting characters:
Step 1: Clarify Function
You can determine which supporting characters are needed and create ways they will serve the narrative through-line (the things they will “do” in the story) once you have a clear understanding of their function and purpose. The supporting character’s function may be to:
Move the Story Forward
For example: In The Sixth Sense, Dr. Malcolm Crowe (Bruce Willis) needs a dead-people-seeing kid (Cole, played by Haley Joel Osment) to move him toward discovery and redemption. Marty McFly (Michael J. Fox) needs supporting character Dr. Emmett Brown (Christopher Lloyd) to help him get Back to the Future.
Define the Protagonist
For example: In Liar, Liar, the supporting character Max (Justin Cooper) helps define Jim Carrey’s character (attorney Fletcher Reede) as a self-absorbed, dishonest man, and a negligent parent – and the ongoing interaction between the two characters helps reveal the hero’s subsequent transformation.
For example: The character of Newt in Aliens is used effectively to expand upon the theme of “motherhood” woven throughout the story.
Step 2: Create Contrasts
Contrasting the main character’s and supporting characters’ feelings, attitudes, lifestyle, opinions, and choices helps create conflict and complications, adds texture, and allows alternate points of view to be explored. For example: In Star Wars, supporting character Han Solo (a daring, reckless, world-weary, “I don’t care about anyone but me” smuggler), contrasts sharply with protagonist, Luke Skywalker (a straight-arrow, clean-cut, idealistic but inexperienced farm boy).
Step 3: Add Details
It’s the small, well-defined details that help create realistic and memorable supporting characters, from the calm, in control, matter-of-fact demeanor of Winston “The Wolf” Wolfe (Harvey Keital) in Pulp Fiction to the sarcastic, complaining, and bungling but deadly nature of Carl Showalter (Steve Buscemi) in Fargo.