For those of you not familiar with Twelfth Night , it is one of the many plays featuring a girl who, for some obscure reason, decides to dress up as a boy, with the requisite hysterical consequences.
In Twelfth Night, Viola pretends to be the boy Cesario and, on the whole, does a really rotten job. Even taking into account the fact that Viola would originally have been played by a boy, all the characters in the play keep commenting on how woman-like "he" is. Viola doesn't do herself any favors by repeatedly dropping huge hints like "I am not what I am", "I am all the daughters of my father's house", "I am almost sick [for a beard], though I would not have it grow on my chin", and so forth.
Fortunately for her, the other characters appear to have all the perceptive abilities and deductive insights of a twig.