Adding a female character to the cast to balance the gender ratio. A female character added to a new season, spinoff, or sequel to balance out the sexes. If she's the first woman in a previously all-male cast, this is just The Smurfette Principle at work and she's probably The Heart. But if she's added when there's already a (single) woman in the cast, to counter the Smurfette Principle by adding more gender balance, then she's an Affirmative Action Girl.