How to Create a Side Character Readers Will Be Obsessed With
You know the feeling. You finish a book and the first thing you do is search for fan art of the sarcastic best friend. Or the morally questionable mentor. Or the rival who only showed up in three chapters but somehow stole every scene.
Side characters like these drive reader engagement. They generate comments, fan theories, and word-of-mouth recommendations. They make readers buy the next book just to see what happens to them. And if you're smart, they become spin-off material that extends your series and your income.
So how do you create one? Not by accident. Here's how to do it on purpose.
Why This Matters for Your Career
Before we get into craft, let's talk business. Obsession-worthy side characters are money.
They drive engagement. Readers who fall for a side character comment more, share more, and stick around longer. If you're serializing, that translates directly to Patreon conversions and subscriber retention.
They create spin-off potential. A beloved side character is a ready-made protagonist for your next book or series. That's not just creative convenience. That's a built-in audience for your next launch.
They generate word of mouth. People recommend books because of characters, not plot. "You have to read this, there's this guy who..." That sentence has sold more books than any ad campaign.
They build fandom. Fan art, fan fiction, character playlists, aesthetic boards. All of that is free marketing. And it almost always centers on side characters, because readers project onto protagonists but fall in love with the people around them.
Now let's build one.
Give Them a Life That Exists Without Your Protagonist
The fastest way to make a side character feel like furniture is to have them exist only in relation to your main character. They show up when needed. They dispense advice or comic relief. They disappear when the scene ends.
Readers sense this. It makes the character feel thin, functional, forgettable.
The fix: give them wants, problems, and a trajectory that have nothing to do with the protagonist's story.
Your side character should have something they're working toward. Something they're worried about. Something they're hiding. These don't need to take over the book. They just need to exist, and occasionally surface.
When your protagonist walks into a scene, the side character was already doing something. They have opinions about things unrelated to the plot. They make choices based on their own priorities, which sometimes conflict with what the protagonist needs.
Try this: Before writing a scene with your side character, answer three questions. What do they want right now that has nothing to do with the protagonist? What are they worried about? What were they doing five minutes before this scene started?
You won't use all of this on the page. But your readers will feel it.
Make Them Weirdly, Specifically Themselves
Generic side characters blend into the background. Specific ones stick.
Specificity means details that feel particular to this person. Not "she was nervous," but the exact way she shows nervousness that no one else in your book shows. Not "he had a dark past," but the one weird thing he does because of that past.
This applies to everything: how they talk, what they notice, what they care about, what annoys them, what they order at a restaurant, what they lie about.
The goal is that readers could identify this character from a single line of dialogue, a single gesture, a single observation. They should feel like a real person you might actually know, not a type.
Try this: Write down five details about your side character that are true of them and almost no one else. Not personality traits. Specific behaviors, preferences, quirks. "Always sits facing the door." "Hates the word 'moist' but won't explain why." "Sends voice memos instead of texts because she thinks typing is inefficient."
Use one or two per scene. That's enough.
Let Them Steal Scenes
Your protagonist has to carry the emotional weight of the story. That's a heavy job. It often means they can't be the funniest, the most cutting, the most outrageous.
Side characters can.
Give your side character permission to say the thing your protagonist is too polite or too careful to say. Let them be the one who cuts through tension with a joke, or escalates conflict with a reckless comment, or drops the observation that reframes everything.
This doesn't mean they're always comic relief. It means they're unfiltered in a way your protagonist often can't be. They have less to lose, or they care less about what they lose, or they simply have a mouth that moves faster than their judgment.
Try this: Look at your last three scenes with this side character. Did they say anything memorable? Anything quotable? Anything that made you laugh or wince while writing it? If not, you're underusing them.
Leave Gaps Readers Want to Fill
We know everything about protagonists. Their backstory, their fears, their internal monologue. That's necessary for the reader to bond with them.
Side characters get to be mysterious.
There should be things about them we don't know. Not big dramatic secrets (though those work too), but gaps. Why did they react that way? What happened to them before? What do they actually think about the protagonist?
These gaps invite readers to speculate, theorize, and imagine. That's engagement. That's investment. That's readers in your comments section arguing about what really happened to the mentor's family.
The key is hinting without explaining. Drop a reference to something that happened before the story. Let them have a reaction that doesn't quite fit. Show them lying about something small. Then move on.
Try this: Identify one thing your side character knows or has experienced that you will never fully explain in this book. Let it influence their behavior just enough that readers notice. Then leave it alone.
Give Them Real Stakes in the Story
Readers don't get obsessed with characters who are just hanging around. They get obsessed with characters who matter.
Your side character needs to affect the plot. Not just react to it. They should make choices that change things. They should have something to lose. At some point, the story should turn on something they do or don't do.
This is different from being useful. A useful side character gives the protagonist information or helps them in a fight. A side character with stakes has their own skin in the game. The outcome matters to them for their own reasons.
Try this: Ask yourself: if this side character disappeared from the book, what would break? Not just "the protagonist would be sad" but what plot element, what necessary function, what turning point would fail to happen? If the answer is nothing, you need to give them more to do.
Create Friction, Even With Allies
The side characters readers obsess over are rarely the ones who are simply nice to the protagonist. They're the ones with complicated relationships.
Even your protagonist's best friend should have moments of disagreement, frustration, or competing priorities. Even a loyal mentor should have blind spots, old wounds, or beliefs that clash with what the protagonist needs to do.
This friction does two things. First, it makes the relationship feel real. Actual friendships involve conflict. Second, it creates tension that readers want to see resolved. Will they work it out? Will this break them? Readers keep turning pages to find out.
The relationship should shift over the course of the story. It gets closer, then it gets strained, then it gets tested. Something happens that changes how these two people see each other. By the end, they're not in the same place they started.
Try this: Identify what your protagonist and this side character would argue about. Not a plot disagreement, but a values difference. They want the same goal but disagree on how to get there, or they agree on methods but have different reasons. Build one scene around this tension.
The Obsession Test
When you've finished drafting, run your side character through these questions:
1. Could readers identify them from a single line of dialogue?
2. Do they have at least one scene where they steal focus from the protagonist?
3. Is there something about them readers will want to know more about?
4. Do they make a choice that affects the outcome of the story?
5. Does their relationship with the protagonist change by the end?
6. Could they carry their own book?
If you're getting four or more yeses, you've probably built someone readers will remember. If not, you know where to revise.
Turning Obsession Into Income
Once you have a side character readers love, use them strategically:
Bonus content. Offer Patreon subscribers or newsletter readers a short story from the side character's POV. This costs you nothing but writing time and dramatically increases perceived value.
Spin-off planning. If readers are clamoring for more of this character, that's market research. Plan a book around them. Announce it. Use the existing demand to fuel your launch.
Engagement bait. Ask readers questions about the character on social media or in your newsletter. What do they think happened in their past? Who would they cast in the movie? This drives comments and shares.
Merch potential. Characters readers obsess over are characters they'll buy merchandise for. Quotes, art prints, themed items. If you're at the scale where merch makes sense, side characters often outsell protagonists.
Let’s Do This
Side characters who capture readers aren't accidents. They're built. They have their own lives, their own specificity, their own mystery. They steal scenes and affect plots. Their relationships with the protagonist evolve and sometimes strain.
This takes more work than writing a functional supporting cast. But the payoff is real: engagement, word of mouth, fandom, and a character who can carry your next book when you're ready to write it.
Think about the side characters you've loved. The ones you searched for fan art of. The ones you wanted a whole series about. Now go build one.
