I have two favorites in fiction.
I really like the sidekick, a comrade who not only boosts but sticks with the lead, no matter what twists the story takes. They're Lucy's Ethel, Charlie Brown's Linus, Frodo's Sam Gamgee. Sidekicks help leads find their next steps. They make leads laugh. They see silver when the lead sees lead. Every lead welcomes a sidekick.
But I love-hate the foils, those persons who frustrate the lead. Foils can be villains, as is Jean Valjean's Javert. But there are myriad others just as willing to keep a lead from what she wants: the unflappable telemarketer, the academically bullying teacher, the over-confident boss, the cranky cashier, the fender-bendering teenager. But even foils can be foiled. By contrast, foils make the lead seem better.
Let's be honest: you and I want more sidekicks, fewer foils. But since most of us get one or two sidekicks and a lot of foils, why not put them to work in fiction?
Foils serve your story. They create conflict. They worry your readers, slogging along with your lead and cheering him to the very last page. Foils make your story ring true: your readers know these people. They may even share a refrigerator with some of them. But foils can do a greater work for your lead. They reveal the lead's character. They sharpen your lead's objective. Best of all, they hone your lead, forcing him or her to develop.
Mine your everyday foils--your co-worker firing verbal potshots, your preschooler doing a little shopping of his own as you skim a grocery aisle, the driver in front of you braking before you have time to, the manipulating tack of your long-lost cousin--and let your lead tackle the challenges they present.
So who is your sidekick? Thank God for him or her. And who are your foils? Maybe list only today's. Then consider offering them positions on the lead--and writer--shaping machine.