Literature is rife with characters that make a large splash with just one dive. In F. Scott Fitzgerald’s The Great Gatsby, Meyer Wolfsheim, Gatsby’s business associate, appears only briefly, but his presence sheds light on the seedy side of things, and we infer that this is where Gatsby earned his fortune.

Don’t worry how many appearances a minor character makes. Instead focus on his or her influence. In some scenarios, the minor character may get a bit of time on the page. Let’s say Crystal and Frank are getting married in three days. Crystal’s ex-husband, Hammond, takes her to lunch, and their conversation makes Crystal doubt her decision to marry Frank. Hammond may only appear in that one scene—which might be a lengthy scene—but his presence is felt throughout the story. That night, Crystal reconsiders Hammond’s words, gestures and actions, parsing them for meaning. She thinks about their blissful trip to the Bahamas while she is finalizing the seating arrangements for the wedding with her future mother-in-law. She dials Hammond’s number the night before the wedding, but hangs up before he answers. As she walks up the aisle, she scans the crowd for Hammond. In fact, her response to his absence—relief or disappointment—may be the very climax of the story.

In other scenarios, the important secondary character may have a less prominent—but still pointed—presence. Let’s say Linda hasn’t spoken to her sister, Grace, in over a year. Linda always felt belittled by Grace, overwhelmed by Grace’s anger toward her. Last time they spoke, Grace stole eighty dollars from Linda and borrowed her car and left it at the state border three hours away. Linda considers checking up on her sister after a call from Grace’s landlord about past due rent. On the day she plans to visit, Linda stops for lunch at an outdoor café. She witnesses an angry man yelling at a timid young waiter. She’s unsettled by this; later the incident comes to mind as she sits in her car outside Grace’s apartment building. She thinks of the angry man’s red face, of the weight of this anger on the young waiter’s shoulders. This makes her decide to drive away from her sister’s apartment. Linda’s time with the angry man and the waiter is fleeting. She doesn’t even interact with them. But the interaction between the angry man and the waiter influences a major choice for Linda.

Interestingly, some stories have important characters that never appear. Susan Glaspell’s short story "A Jury of Her Peers” tells the story of two women in the kitchen of Minnie Wright, a woman suspected of murdering her husband. The women in the kitchen find compelling evidence of Minnie’s guilt and they must decide whether to reveal their findings. The character of Minnie—her personality, actions and emotions—is crucial to the women understanding the evidence in front of them, yet Minnie sits in jail, unseen, as the story unfolds in her kitchen.