Avi's novel The True Confessions of Charlotte Doyle and the movie Mulan are set in very different times and places, and their plots are also quite distinct, yet the characters in the two works do share many important traits.
Charlotte Doyle and Mulan, for instance, both step out of their normal roles as girls and pursue what would usually be considered the paths of men and boys. Charlotte becomes part of a ship's crew. She learns how to climb the rigging and do all the work necessary to keep a ship afloat. In the process, she shows herself to be incredibly brave and resourceful. Mulan, too, strikes out in a new way and trains to join the Chinese army to fight against the Huns. Unlike Charlotte, she disguises herself as a young man, but like Charlotte, she, too, proves to be outstandingly brave and resourceful as she devises and carries out plans to defeat the Huns' leader, Shan Yu.
Both Charlotte and Mulan are determined to stand up to and defeat evil. Charlotte plots against Captain Jaggery and confronts him to save the ship and its crew. Mulan faces the terrible Shan Yu and in the end, plots against him and saves the nation and her people. Both young women confront their fears as well and conquer them, which may indeed be more important than facing down a terrible human enemy.
There are certainly similarities between the villains in the two stories also. Captain Jaggery and Shan Yu are both brutal men who lead by fear. Captain Jaggery once beat a man so badly that he lost an arm, and he seems to beat Zachariah to death. He even murders his first mate, Mr. Hollybrass, for arguing with him and then blames the deed on Charlotte. Indeed, Jaggery cannot tolerate questioning or opposition from anyone. The same may be said of Shan Yu, who kills innocent people without a second thought, including women and children in the villages he massacres. His soldiers are terrified of him, and he will tolerate no disobedience or weakness in battle. Anyone who dares cross Shan Yu ends up dead. Both of these villains, however, encounter opposition from the unexpected source of two young ladies who, while afraid, will not be oppressed by these men.