When a character doesn’t change and is fairly uncomplicated, it is said to be a flat character. Its opposite is a round character, which has dimension and develops over the course of the story.

Typically only one or a small number of round characters appear in a story, and they usually are the protagonist or main characters. Virtually all of the other characters will be flat by necessity. That’s because their main purpose is to move the story along. After all, you may need a cop directing traffic on a street that our main character desperately must get down; the cop need not be developed or have any other traits than those typical of one directing traffic – a firm stance, blowing a whistle, maybe fluid motions with his arms and hands.

Despite being so simple, there are a couple of variations on flat characters.

A cardboard character is unreal due to its superficiality. A good example would be the cut-out Mary Sue cliché of fan fiction in which the character is an everyday, lonely woman who has a good heart. Another is red shirt of “Star Trek: The Original Series” in which the character wearing that colored uniform usually is the one who dies in a scene. Typically readers find such characters annoying.

A background or stock character is one whose traits are merely provided to that the reader know what his or her job is. Such a character – like the aforementioned policeman directing traffic – merely appears in a story to move along the action. Novelist Henry James called them ficelle characters while Vladimir Nabokov called them peri characters.

A static character remains the same throughout the story, meaning it does not grow or develop; typically they appear several times in a story rather than just once as the previously mentioned policeman directing traffic. Its opposite is a dynamic character, which also is a round character. An example of static characters are Rosencranz and Guildenstern from “Hamlet.”