Pitt and Damon will both be voicing characters in Miller's Happy Feet 2, a 3-D sequel to his 2006 animated film. They’ll be joining original cast members who include Robin Williams and Elijah Wood.
Warner Bros. refused comment on the casting, but sources say that it's a done deal — in fact, both Pitt and Damon were recording for it this week.
Happy Feet 2 is currently set for release on November 28, 2011.
Source: Movie Line