How Optimus Prime Got His Iconic 'Gentleman's' Voice Instead Of Being A Yelling Drill Sergeant

Few animated characters and the voice actors behind them feel as inseparable as Optimus Prime and Peter Cullen. A few have similar claims to the title — the late, great Kevin Conroy with Batman, for example. But even though others have had brief tenures behind the mask of the Autobot leader, when you think of the Transformers franchise writ large, you likely think immediately of that stoic, measured, robotic tone.

Autobots, transform and roll out.

It's the quiet gravitas, the almost sage-like quality of the voice, that made it instantly so iconic.But while we can all agree on the timeless quality of the result, accounts vary somewhat on how Cullen actually arrived at the final voice for Optimus.

"I was pushing him pretty hard at that audition," voice director Wally Burr told Topless Robot in 2015, referring to Cullen's original tryout for the part. Apparently, Cullen was recording a long string of promos the next day for ABC and asked to pull back a bit on his vocal intensity. "And I said, 'What if we back off a lot and just make Optimus a very nice gentleman who doesn't shout at anybody, because he knows what the hell he's doing?'" Burr said. "And so Peter softened his voice, and became noble! Instead of a shouting boss, he was noble."

While that story seems to be true — with Burr claiming Cullen has since thanked him publicly for the push — Cullen has attributed the voice of Optimus to a different key inspiration: his brother Larry, who served as a captain in the U.S. Marines.

Two things can be true at the same time. Voice auditions can go all over the place, so it makes sense that Cullen and Burr would have tried a range of things during the former's audition for "Transformers," ultimately leading to a quieter, more "noble" sound, as Burr claims. However, Cullen has said on multiple occasions that he went into the audition with that quieter gravitas in mind, due primarily to a conversation he had with his brother beforehand. A veteran of the Vietnam War, Larry Cullen had a profound impact on his brother when he returned from that tour of duty.

"When he came home, I could see a change," Cullen told Zap2it in 2006. "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."

Cullen told a slightly different version of the story at TFcon 2015 when asked by a fan how he came up with the voice. At the time of the audition, the brothers were living together, and Peter jokingly told Larry the day he went up for the part that he was "auditioning as a truck." When he explained the heroic nature of the character, however, his brother gave him some simple advice: "Be strong enough to be gentle." And so, Optimus Prime was born, directly inspired by the elder Cullen.

The original "Transformers" cartoon premiered in 1984. Since then, Peter Cullen has voiced Optimus Prime in dozens of movies, shows, and video games, from the live-action Michael Bay "Transformers" movies (all the way up through 2023's "Transformers: Rise of the Beasts") to more modern animated adaptations like "Transformers: Robots in Disguise" and "Transformers: Prime" — the latter of which earned Cullen a Daytime Emmy nomination.

Plenty of other very talented actors have spent time in the role — noted vocal savants like Alan Tudyk and David Kaye, and most recently, Chris Hemsworth, who did a solid job as a younger version of the Autobot in 2024's "Transformers One." But while they've all done fine work, Cullen's original performance, brought back again and again, is Optimus, and to hear him tell it, he has his brother to thank.