Ask Henry Winkler about his longstanding personal and professional relationship with Ron Howard, and the adjectives roll out: “an amazing fellow,” “incredibly perceptive” and finally, “I love him.”

The effusiveness is no Hollywood puffery: Winkler and Howard forged an instant friendship while co-starring in the ABC sitcom “Happy Days” from 1974 to 1980 that has lasted for more than 40 years. Though Howard was 10 years younger than Winkler. who played the Fonz, at the time, he was immediately struck by his confidence and innate selflessness as a creative collaborator.

“I knew that wherever my imagination went, he would be there,” Winkler says. “We could memorize a scene, rehearse it, shoot it and improvise it in 20 minutes. As an actor, you felt safe with Ron.”

As Winkler notes, those qualities also defined Howard as a filmmaker. Both Howard and Winkler began their first forays behind the camera — Howard as director on “Grand Theft Auto,” and Winkler as producer and narrator of the Oscar- and Emmy-winning documentary “Who Are the DeBolts? And Where Did They Get Nineteen Kids?” — while working on “Happy Days” in 1977.

“We chatted about it while we were waiting for a scene. He said, ‘Do you think I could be a good director?’” says Winkler. “I said, ‘Ron, you could probably be a great brain surgeon, if you put your mind to it.’ (He had) confidence and humanity and will and perception, because telling a story is knowing the human condition.”

Winkler witnessed Howard’s innate talents firsthand as star of his first studio feature, “Night Shift,” in 1982. (Winkler earned a Golden Globe nomination).

“You’d ask him, ‘I gotta do this, I want to go here’,” Winkler says. “And he would roll the entire film in his head, and think if your idea fit into his vision. And if I was anywhere in its Zip Code, he would say, ‘Yes, we could do that.’ Or, ‘You know, let’s try it this way, and we’ll come back to that.’ There’s not an actor on earth that he can’t talk to or help along to get where he wants to go.”

Since that collaboration, both men have enjoyed diverse careers, with Winkler finding success as a producer, director and the author of 31 novels for children (the popular and endearing Hank Zipser series) in addition to acting. But the bond between them remains as strong as it did on the set of “Happy Days,” and is now linked by family: Winkler is the godfather of Howard’s daughter, actress Bryce Dallas Howard. And even in this regard, their relationship is marked by respect and humanity.

As Winkler remembers, “Early on, he said to us, ‘God forbid, if anything happens to us, would you take all of our children. You can even bar mitzvah them.’ I thought that was one of the great compliments of my life.”