For millions of Americans, Peter Cullen’s face may not have been instantly familiar.

But his voice almost certainly was.

Peter Cullen, the legendary performer who gave Optimus Prime his unmistakable voice in Transformers and brought the gloomy but lovable Eeyore to life in Winnie the Pooh, passed away Wednesday at his Los Angeles home. He was 85.

His agent confirmed the news, while Cullen’s family said he passed peacefully surrounded by those he loved. No official cause has been announced.

For viewers who grew up in the 1970s, ’80s and ’90s, Cullen’s career stretches through an astonishing amount of pop-culture history.

He first became Optimus Prime in the original Transformers animated series in 1984. His deep, calm voice helped transform the Autobot leader from a cartoon robot into a character generations of children viewed as a genuine hero.

And there was a deeply personal reason Optimus sounded the way he did.

Before Cullen’s audition, he spoke with his older brother Larry, a Marine veteran whom Cullen considered his hero. Larry encouraged him not to portray a hero through shouting and bravado, but through compassion and quiet strength.

Cullen carried that idea into the audition — and Optimus Prime was born.

Decades later, Hollywood brought Transformers to the big screen, and there was still only one voice many fans wanted to hear. Cullen returned as Optimus for the 2007 blockbuster and continued voicing the character through multiple films, including 2023’s Transformers: Rise of the Beasts.

But Optimus was only one part of his remarkable career.

Cullen was also the voice of Eeyore, the melancholy donkey from Winnie the Pooh. Older television viewers may remember him as the voice of KARR, KITT’s dangerous rival on Knight Rider. He also created vocal sounds for the creature in Arnold Schwarzenegger’s 1987 classic Predator and worked on everything from The Smothers Brothers Comedy Hour to Chip ‘n Dale: Rescue Rangers.

In 2023, Cullen received a Lifetime Achievement Award at the Children’s & Family Emmy Awards.

Perhaps the most moving words following the news, however, came from his family.

They asked fans to honor Cullen by showing compassion, integrity and loyalty to others — and to remember the principle that helped shape his most famous character:

“Be strong enough to be gentle.”

Peter Cullen spent much of his career behind a microphone.

But after more than five decades of unforgettable work, millions of people will recognize that voice forever.