But when I think that this story is not just in this setting, but features a minor character from another story. Except then I have to consider whether it works. Particularly a bit character who was therefore strongly and narrowly characterized, to flash brightly, and it didn't matter that the character was one-note.
A series can be a superior work of art by containing all of its part, just as a cathedral can unify all its statuary and stained glass to something more. But you do have to unify it.