 Screenwriter Michael Arndt worked for a year on the film 's script , calling it " both a brilliantly creative idea but also incredibly challenging , " but left the project in early 2011 , adding that " knowing the Pixar process , there may not be a single word [ I wrote ] that remains in the final script ! They 've had writers work on it since then . " Despite his departure , Arndt received an ' Additional Story Material ' credit . 
