How Optimus Prime's Original Voice Actor Convinced Michael Bay To Cast Him In Transformers

You might not know the name Peter Cullen, but I guarantee you know his voice. He's Eeyore in the "Winnie the Pooh" franchise, Monterey Jack in "Chip 'n Dale Rescue Rangers," the first voice of KARR in "Knight Rider," the vocalizations of the titular "Predator," and since he voiced Mario in the Donkey Kong segments of "Saturday Supercade," he's actually the first person to ever give Mario a voice in the English-speaking world. All of these roles border on iconic, but Cullen became a living legend by providing the voice of Optimus Prime in the "Transformers" franchise.

In 2022, for the film's 15-year anniversary, Paramount held an event celebrating all things "Transformers," and Peter Cullen spoke (via Comic Book Resource) about his journey from voicing Optimus Prime in the animated series to bringing the character to life in live action. Despite Cullen's history with the series, he still had to audition for the role of Optimus Prime like everyone else. "When I first auditioned for [director] Michael [Bay], a young gal was going to read the lines of the other character," Cullen said. "We looked at the script, and it said 'Ironhide.' I actually played Ironhide in the cartoon series as well."

Realizing this could give him an advantage over everyone else, Cullen asked if he could read both sets of lines, alternating between Optimus Prime and Ironhide. Bay was stunned by the ask, not realizing that this is a pretty common practice for many voiceover artists. "Frank Welker, one of the great voice actors of all time, he'd do Megatron and like five other voices," said Cullen. "So we always ended up talking to ourselves."

The move proved to be effective. Bay was impressed and asked Cullen to focus on the voice of Optimus Prime, later bringing him back for additional auditions before finally making the right call and giving Cullen the role. "[Bay] always had a really big smile on his face," Cullen said. "It was just interesting to see how [my voice] was going to fit how big Michael's concept of a 45-foot statue, how it was going to fit my voice. He was like, 'How are we going to make that adjustment?' So I said, 'We'll just go lower.'" Eventually, Jess Harnell ("The Animaniacs," "Crash Bandicoot") was given the voice of Ironhide, a role he held throughout the first three films in the series.

Peter Cullen has rightfully maintained the role of Optimus Prime in the subsequent "Transformers" films ever since and helped educate Bay on the world of Autobots and Decepticons. "He would always be very happy," said Cullen. "He didn't know much about the characters beforehand, but he certainly learned quickly." That crash course has certainly proved beneficial, as the "Transformers" films have only gotten better with each installment. And no matter who sits in the director's chair, Peter Cullen has consistently kept Optimus Prime alive.

That is ... until the upcoming "Transformers One," animated prequel where Chris Hemsworth will be taking on the voice of Optimus Prime. He joins an exclusively (thus far) celebrity cast, including Jon Hamm as Sentinel Prime, Brian Tyree Henry as Megatron, Keegan-Michael Key as Bumblebee, Laurence Fishburne as Alpha Trion, and Scarlett Johansson as Elita.

They've got some mighty big shoes to fill.