Let's stick with the grown women playing young boys theme and introduce Pamela Adlon. Though she's an actress in her own right, Adlon is best known as the voice of Bobby Hill from King of The Hill (for which she won an Emmy Award). Adlon is one of those rare Hollywood oddities: someone who started as a child actor, worked consistently, and has enjoyed success without becoming paparazzi fodder. There's so many ways it could have gone wrong, but Adlon has remained on top through hard work and talent.
You may also recognize her as the voice of Ashley Spinelli on Recess. Her other work includes playing Otto Osworth on the series Time Squad and also starring in the series Better Things. Adlon is a woman of many talents, not just an actor. She's also a screenwriter, producer, and director.