John Goodman and Ken Watanbe were announced as voice actors for Transformers 4: Age of Extinction on May 8.

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This might seem suprising to fans as the film release is right around the corner, but a lot of times films which use CGI and non-human characters, some voice work is left for later. Goodman will be voicing the Autobot Hound and Wantanbe will portray Drift. The other voice cast members include Frank Welker as Galvatron, John DiMaggio as Crosshairs, Mark Ryan as Lockdown, Robert Foxworth as Ratchet, and Reno Wilson as Brains.

Peter Cullen, who has been the voice artist for Optimus Prime over all these years will be reprising his role in the film.

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In the April 27 interview with USA Today, Cullen stated that his inspiration while voicing the iconic character came from his brother Larry, who had served in the Vietnam war and died in 2011.

"Though Larry's gone," Cullen said, "he lives on in my mind as Optimus Prime because he was my hero."Cullen has been voicing the character for over 3 decades now, starting with the Transformers cartoons in the Eighties.

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Interestingly, Bay has been suggesting that Age of Extinction will give a fresh start to the series and that Optimus Prime will also be undergoing some changes as he starts to lose faith in the goodness of mankind. But Cullen believes that even faced with these challenges Optimus Prime will stay strong and his most valuable traits will endure."He is exactly who he was from the very original concept," Cullen said. "I've always felt a hero should have the qualities that are inspiring and helpful and fatherly and at the same time (be) courageous. I don't see those character traits changing at all."

Cullen's son Clay is also a stuntman in Age of Extinction.

Transformers: Age of Extinction will hit theaters on June 27, 2014.

Watch a trailer for the film here: