Smurfette principle

The Smurfette principle is the practice in fiction, such as film and television series, to include only one woman in an otherwise entirely male ensemble. It establishes a male-dominated narrative, where the woman is the exception and exists only in reference to the men. As a consequence, works employing this trope often fail the Bechdel test, an indicator of gender bias in fiction.

The term was coined by Katha Pollitt in 1991 in The New York Times:

"Contemporary shows are either essentially all-male, like "Garfield," or are organized on what I call the Smurfette principle: a group of male buddies will be accented by a lone female, stereotypically defined... The message is clear. Boys are the norm, girls the variation; boys are central, girls peripheral; boys are individuals, girls types. Boys define the group, its story and its code of values. Girls exist only in relation to boys."