The New Kid is the main protagonist of the game and the player's avatar throuought the entire game. You can create him in the start of the game after Cartman's introduction of the war between the humans and the elves.
The New Kid looks like anything you want him/her to be like.
The New Kid was predicted by Cartman to arrive and end the war between the humans and the elves.
He is really an entity that can create a huge number of friends in a short amount of time. His parents deciced to move to South Park to escape the government who wants to use him.
The New Kid says absolutely nothing until the end of the game.