While Natalie Portman plays Padmé Amidala in Star Wars Episode I: The Phantom Menace, she does not switch places with the Queen.
Here's what actually happens:
* The character of Padmé Amidala is the Queen of Naboo.
* She is the one who travels to Coruscant, the capital of the Republic, to plead for help from the Jedi.
* She disguises herself as a handmaiden named "Sabé" to protect her identity from Separatist forces.
* Sabé actually does become the public face of the Queen while Amidala works behind the scenes.
There are a few reasons people get confused:
* The handmaiden disguises are very convincing.
* Sabé is given prominence in some scenes.
* The film is a bit ambiguous at times about who is actually the Queen.
But Natalie Portman never switches places with the Queen. The actress portraying Sabé is Keisha Castle-Hughes.