Peter Cullen's Final Role Was On A Current Hit Superhero Series

Legendary voice actor Peter Cullen died on Wednesday, August 26, 2026, leaving behind a long list of memorable characters. He was best known for playing Optimus Prime in the "Transformers" franchise across animated shows, live-action movies, and video games. But his final role was in one of the best superhero TV shows of all time: "Invincible."

The animated Prime Video series follows Mark Grayson (Steven Yeun), who develops super strength and the ability to fly thanks to his alien father, Nolan, aka Omni-Man (J.K. Simmons). However, after a game-changing twist, Omni-Man is revealed as a villain sent by the Viltrum Empire to conquer Earth. Mark later joins forces with the Coalition of Planets, a galactic alliance led by Cullen's character, Thaedus.

Thaedus is introduced during Season 2 and becomes a key player in the fight against the Viltrum Empire. Cullen uses a deep, booming voice for the character, fitting Thaedus' role as the Coalition's leader.

"Transformers" was a formative franchise for "Invincible" creator Robert Kirkman, which made collaborating with Peter Cullen especially meaningful. "Working with Peter Cullen was a huge test for my professionalism," Kirkman told Polygon. "Just flat-out, every fiber of my being was screaming, 'Don't ask him about Optimus Prime ... Just be a professional, come on.'"

He explained that the show recorded lines with the cast over Zoom, and he kept his camera off during these sessions. Kirkman said he was grateful for the decision because he was getting teary-eyed. "I've been hearing Peter Cullen's voice since I was like 7 years old. So to have him voicing the character he voices — it's crazy to have written dialogue that's coming out of his mouth," he added.

Cullen voiced Thaedus again in "Invincible" Season 4, released in 2026, making the Prime Video series his final credited project before his death in August.