People talk a lot about protagonist, antagonist, secondary characters, and sidekicks when it comes to writing. When writing a series, you can have a big cast of characters that fall into these characters. You can also have a small group of recurring minor characters. I might be misinterpreting what Misha suggested here, but I’m going with the background guys that you can still notice. Like ‘Cabbage Man’ or whatever Last Airbender fans call him. I’ll touch on a more serious versions too, so I cover all bases.
- Comedy– Many times you’ll find a minor character returning for laughs. They’re bad luck incarnate who happen to be at the wrong place at the wrong time. Hit by a stray spell or lose their third house to the main characters. Maybe they keep getting captured by the villains and ending up in a dungeon whenever the heroes have to sneak into a lair. The key here is to have the character interact briefly with the major characters, but not be plot essential.
- Shop Owners– Every time the characters need supplies, they go to a store and talk to the shopkeeper. After a few times, a reader realizes that it’s the same guy. This can fall into comedy or perceived as laziness on the part of the writer. Yet, it can also help your world with an odd piece of continuity. It shows a character is moving around the world and developing a business chain. This can also be a fun treat for readers who are paying attention.
- Small Time Crook– I’m noticing that a lot of these will have a comedic approach, but this one can be serious. A nameless pickpocket or bandit that runs into the heroes at times. They can always fail or even become a brief plot point where they take an important item. These characters can create a sense of the world having a criminal element that isn’t at the epic proportion level. This is depth and makes the fictional world feel more believable.
- Old Friends– Many series have those characters that shift from main supporting cast to no longer around. In Legends of Windemere, Selenia Hamilton and Kira Grasdon would fall into this. They play big roles in the first book and barely appear in the second book. By the third, neither of them are around except by name. This creates the opportunity for ‘The Grand Return’. A character in this category can be brought back in with some fanfare and get readers pumped. They think that something big is about to happen if one of these characters is back. In terms of Selenia, it means a battle might ensue. With Kira, it means Luke Callindor’s love life is about to take center stage and he’ll be praying for the Lich to appear. The point is that this creates an atmosphere of suspense and tension birthed from excitement.
- Cameo– The final category that I can think of is when a main character from another series or the previous books appears in a minor role. You typically find this in long series, comics, or an author’s new series. These character usages are nods to the previous work and gifts to loyal fans. Though, it can also be done to lock in fans for a new series. That might seem necessary if the author or the fans are having trouble letting go of the past.
There might be a ton of categories for these characters and they’re flexible enough that you can do nearly anything with them. If the story is write, you can even have a character that dies every time they appear. This was done in the God of War video game series with a luckless Boat Captain. Again, these tend to be humorous Easter Eggs for those that are paying attention.