On Severance, Lumon corporation’s Dr. Mauer, played by Robby Benson, is the testing floor’s chameleon.

“I had four wigs, aside from all of my beards and mustaches,” Robby says of the enigmatic character who is Gemma Scout’s jailer, torturer and greatest admirer. “I’m almost 70, so this is my sixth decade of working, and I’m really proud of the work I did in Severance,” he exclusively tells Closer.

For fans of Robby’s starring roles in film and theater, Dr. Mauer feels like quite a departure.

“I always did kind of play the boy next door,” Robby, 69, says of his younger years.

But he’s also the rare performer who has never been famous for just one thing. Over the decades, Robby’s acted, written scripts, released music, directed popular TV series, taught and authored books. Despite his early success, he never suffered the teen idol label.

“I think a lot of it had to do with coming from New York and theater,” he explains. “I’ve never had a problem being taken seriously.”

A lot of people may not realize how young you were when you started working.

I started [my] first job in theater when I was eight years old. I was one of the kids in The King and I. At 10, I was Oliver in Oliver! When I was 12, I was co-starring in a Broadway show called Zelda with Ed Begley — that’s Ed Begley, not Ed Begley Jr. He was a remarkable actor.

You also started writing early.

My father was a writer. When I was young, that’s all I used to do. When I was 18, I sold a script to Warner Brothers called One on One. It was pretty successful. We just got lucky.

That’s pretty amazing.

I’ve really had a wonderful career. I went back to Broadway to do Pirates of Penzance. That’s where I met my wife, Karla DeVito, who played Mabel. We got married after I begged her for a year! And now we’ve been married for 43 years.

Aww! But it hasn’t been all smooth sailing. You’ve written about the four open-heart surgeries you’ve undergone to treat a congenital heart valve defect.

In my mid-20s, right after we had our first baby, I needed my first open-heart surgery. It changed the direction of everything. I had to completely reinvent myself, so I started directing and teaching.

Did your health issues give you a new appreciation for life?

It gave me an appreciation for the things that I had. Karla and I had children and I had to make a living in different ways. I started teaching at the university level and I would bring my students to sets to show them what it’s really all about.