Though the major roles in the reboot of 'Fantastic Four' have been filled, the movie must do some world-building to set up the film's already dated sequel. So it's no surprise that Tim Blake Nelson is joining the cast of the film to play Harvey Elder, who will eventually (though not in the first film) become the Mole Man.

The Hollywood Reporter broke that Josh Trank's version is in final talks to add Nelson to the movie, likely playing a friend and/or possible mentor to Miles Teller's Reed Richards/Mr. Fantastic. He would then join Teller, Kate Mara's Sue Storm/Invisible Woman, Michael B. Jordan's Johnny Storm/The Human Torch, Jamie Bell's Ben Grimm/The Thing and Toby Kebbell's Dr. Victor Von Doom.

Tim Blake Nelson became a popular character actor after his breakout performance in the Coen Brothers' 'O Brother, Where Art Thou,' though he is also known for his time behind the camera directing films like the modernized 'Othello' adaptation 'O' and 'Leaves of Grass.' But what makes this most notable is that if Nelson accepts this role, it will be the second time he'll play a character in a Marvel movie that's set up to have a bigger part in a possible sequel: In 'The Incredible Hulk' Nelson played Samuel Sterns, and was poised to become The Leader. Alas, that film did not inspire a sequel. 'Fantastic Four' is scheduled to hit theaters June 19, 2015.

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