In pantomime, a principal boy role is the young male protagonist of the play, traditionally played by a young actress in boy's clothes.
The tradition grew out of laws restricting the use of child actors in London theatre, and the responsibility carried by such lead roles. A Breeches role was also a rare opportunity for an early 20th Century actress to wear a revealing costume, potentially increasing the size of the audience [1] The practice of having a female play the principal boy was becoming less common in the late 20th century, as further outlets were sought for the talents of young male pop stars and actors.
Although not written as a pantomime, Peter Pan, or The Boy Who Wouldn't Grow Up is often produced as one with the tradition of a female principal boy continuing.