There are many people behind the toys and games we love—inventors, designers, engineers, marketers, executives and countless others whose names may or may not ever appear on the box. And sometimes someone comes along who gives a toy something that can't be molded from plastic.   A voice. A personality. A heart.   Peter Cullen did that for Optimus Prime. Cullen, the legendary voice actor who brought Optimus Prime to life beginning with the original Transformers animated series in 1984, passed away Wednesday at his home in Los Angeles at the age of 85. His extraordinary career spanned six decades, but for generations of children and adults around the world, that unmistakable voice will forever belong to the leader of the Autobots.   And the story of how Cullen found that voice may be even more memorable than the voice itself. Before heading to his audition in 1984, Cullen told his older brother Larry that he was auditioning to play a truck—a hero truck. Larry Cullen was a Marine veteran who had served in Vietnam, and Peter deeply admired him. Larry offered his younger brother some advice about what a hero should be.   As Hasbro recalled in its tribute to Cullen: “If you’re going to be a hero, be a real hero. Be strong enough to be gentle. Be compassionate, understanding, and be true.”   Peter listened. Years later, he recalled that when he entered the audition booth and read the character description, Larry's voice simply came out of him. Cullen wasn't trying to create the stereotypical booming Hollywood hero. He was channeling the strength, dignity and gentleness he saw in his brother. And Optimus Prime was born.   Think about what happened next. Children around the world weren't simply transforming a toy truck into a robot. Through television, movies and storytelling, they knew who that robot was. Optimus Prime was powerful, but compassionate. Strong, but gentle. A leader who didn't need to diminish others to demonstrate his own strength. A hero.   Cullen continued voicing Optimus Prime across decades of Transformers television, movies, games and other projects, including the live-action film franchise. The character became inseparable from the voice—and the voice became inseparable from the values Cullen and his brother had placed inside it. That's an extraordinary contribution to the power of play.   Toys invite children to tell stories. But the stories surrounding those toys can also influence who children imagine those characters to be—and perhaps, in some small way, who they imagine themselves becoming. Hasbro captured that beautifully in its remembrance of Cullen, writing that Optimus Prime “wasn't a character performance for Peter; it was simply a reflection of the man underneath.”    His family offered a similarly fitting request following his passing: honor Peter's legacy through service and by leading others with compassion, integrity and loyalty—and always remember to “be strong enough to be gentle.”    Peter Cullen didn't invent Optimus Prime. He didn't engineer the transformation or manufacture the toy. But he gave one of the world's most beloved toys something equally enduring: Its voice—and much of its heart.   Thank you, Peter Cullen.   Till all are one.