Polly Perks
The main character in Monstrous Regiment. A Borogravian girl of 16 who joined the army under the name Oliver Perks to rescue her brother Paul and save her family's inn. She chose her false name, Oliver, because it corresponded with the folksong "Sweet Polly Oliver", which is about a girl running off to join the army. As a member of the Cheesemongers, Private 'Ozzer' Perks serves with the colourful Sgt Jackrum, a reformed vampire named Maladict, a troll called Carborundum, an Igor, and a few even stranger people, who are, in fact, all women in disguise.
By the end of the book, Polly is a seasoned soldier, and it turns out, not the important one in the unit. At the end of the book, Polly has left the army, but rejoins as a sergeant when Borogravia is invaded again.
Read more about this topic: Discworld Characters