From (TV series)

When he came home, I could see a change. He was quieter and he was a man and a hero to me. I watched him and listened to him. I’d never had an opportunity to do a superhero, and when that came, [that voice] just came right out of me and I sounded like Optimus.

— Peter Cullen, describing in a 2006 interview how he based Optimus Prime’s voice on his older brother Larry, a Vietnam War veteran