Ready, Player One has a great cast already that includes Simon Pegg, Ben Mendelsohn, Tye Sheridan, and Olivia Cooke. Now, Steven Spielberg is bringing back one of his ringers for the film. Mark Rylance worked for Spielberg on Bridge of Spies as well as providing all of the motion capture and voice work for the giant in his upcoming The BFG. Now, the actor has just joined the cast of the Ernest Cline adaptation as James Donovan Halliday, the creator of OASIS, the immersive game platform that not only sets the stage for the entire story, but is also the prize being sought by all the egg hunters.