We've heard from numerous people connected to Transformers 2.
But here's a unique interview: Ain't It Cool recently sat down with Peter Cullen, the voice actor behind Optimus Prime. Here's an excerpt from that conversation:
Q: Was there any inkling when you took on the role of Optimus Prime that this character was going to leave such a profound effect on people?
Cullen: I think so. When I saw the character breakdown, I said, "This is indeed a real hero. This is not like any hero we've ever seen before." He penetrated different zones. There was a sense of him. He wasn't just muscle and strength. He went beyond that. There was dignity and courage, and a soft spoken honor and integrity about him. Very well written.
So to apply those traits... they weren't necessarily implicated in the script; I just did an impression of my brother Larry, who served in the Marine Corps, and lowered the voice. I think we nailed it. The scripts were wonderfully written, and there was so much to absorb in a half-hour.