When talking about the actor John Lithgow, it seems essential to start with one simple question: Exactly which John Lithgow are we interviewing? He is the genial goofball who charmed sitcom lovers in “3rd Rock from the Sun,” the outstanding supporting actor in “Terms of Endearment” and “Footloose,” and the master Thespian in Arthur Miller’s “All My Sons” on Broadway, where he played deeply flawed patriarch Joe Keller. He’s also the author of 10 best-selling children’s books. And he’s headed back to the small screen as the latest villain on Showtime’s series “Dexter.”

Considering the great depth and breadth he displays on stage and screen, Bankrate found plenty to ask Lithgow about, from the wonderful variety in his work to the highlights of his career to the joy of bouncing from television to movies to theater and back again.

Bankrate: You’re the rare actor who keeps equally busy in film and theater. How would you compare the different challenges and pleasures each one provides you?

John Lithgow: On stage, you’re in control of the performance from start to finish. When you do a movie, it’s in little, tiny slivers, and people put it together long after you’ve departed the scene. So theater’s a purer form of acting, I guess … not to sound too pretentious.

Bankrate: If the money in film and theater were equal, would you give up film altogether and just do theater?

John Lithgow: Oh, no. Movies are a completely different kind of adventure, but they’re an adventure, too. The challenge of the movies is the tedium of the actual process. I learned early on that the great challenge of movies is in keeping your mind alert while everybody else lights the set and plots the shots. For every hour you actually work in a day, there’s another 12 hours of waiting. But you go to fabulous places, you work with extraordinary people, and it’s great to be in a big movie when it finally comes out. And then you have television, which is an altogether different beast. It was really, really fun doing “3rd Rock from the Sun.” It was like running wind sprints. You have exactly one week to create a 23-minute, one-act farce. I felt like I laughed for a living.

Bankrate: What drew you to “All My Sons”?

John Lithgow: A year ago I was working in London, rehearsing with the Royal Shakespeare Company, and my agent told me to meet this man, Simon McBurney (the play’s director). I was fairly lukewarm about doing Arthur Miller’s first play, a play that I mostly knew from a pretty mediocre production of it that I’d seen about 40 years ago, but I met with Simon. He’s just an electrifying personality. He gets you so excited about the things he’s excited about. We met one day for about an hour and a half, and at the end of that time, we agreed to get together with a whole bunch of actors and just work the play for an entire day — on my day off from the other job. … Suddenly this play felt so alive and immediate and intense. When the idea came up, I felt I was very miscast for the role of Joe Keller. But in a way, that’s the kind of challenge you look for — something you really can work hard on and surprise yourself.

Bankrate: Throughout your career, you’ve done a great blend of comedy and drama. Which is the most fun to play?

John Lithgow: I guess comedy is the most flat-out fun. You don’t exactly call “All My Sons” a fun experience because it’s such a brutal play. It’s very involving, very fulfilling. But there’s nothing quite as fun as standing on stage during a 15-second-long laugh, a show-stopping laugh. There’s just nothing like that. It’s wonderful. Everyone’s having a good time in a moment like that.

Bankrate: Was there any one role you had in your career that changed your life more than any other?

John Lithgow: I guess there were three life-changing roles because each of them was a debut of sorts. My Broadway debut in “The Changing Room” in 1973 was my first job on Broadway, and three weeks after opening night, I got my first Tony Award, which got me started as a working actor. The second big breakthrough role was Roberta Muldoon in “The World According to Garp.” That was my breakthrough role in films. And then, of course, there was Dick Solomon in “3rd Rock from the Sun,” which took everybody by surprise, myself included. Starring in a hit TV series is a different kind of success altogether. You become such common knowledge.

Bankrate: So is “3rd Rock” the role people most stop you on the street for?

John Lithgow: Oh yes, I think so. When people say, “Aren’t you that guy?” they’re usually talking about “3rd Rock from the Sun.”

Bankrate: What was it before that?

John Lithgow: There are so many. The thing is, I’ve worked in so many different veins that people recognize me for different things. I get recognized all the time for “Ricochet,” “Footloose,” “Garp,” “Terms of Endearment,” “Buckaroo Banzai.” And then you walk through the streets of New York, and every fifth person you meet has just seen you the night before in “All My Sons.”

Bankrate: How do you manage to balance all the things you do?

John Lithgow: It’s just going from one thing to another, really. I only do things when I have time for them. The most important thing in my life is my marriage and my family. That’s at the very heart of things. I guess that’s how I balance it. I’ve always believed that for an actor, it’s vitally important to have other things in your life that are far more important than acting.

Bankrate: So what do you do for fun to get away from acting?

John Lithgow: My wife is from Montana, and we have a little cabin on a lake there, and we disappear there — at least in the summers and oftentimes during the year. That’s an extraordinary retreat. We ride horses, ski in the winter, swim in the summer, play tennis and golf. It’s all the stuff I never gave myself — gifts I never gave myself as a young man. I also paint. Actually, when I started out, late into my teens, I was far more interested in being a painter than an actor, and I maintain that as a hobby. When I’m in LA, I rent a painting studio and disappear there for hours and oil paint.

Bankrate: Do you treat yourself to any great extravagances?

John Lithgow: My biggest extravagance was finally getting myself a beautiful apartment in New York. I’ve lived in Los Angeles since the ’80s — my wife is a UCLA professor there — and I’ve come back many, many times to do jobs in New York. But I was always scaring up a sublet somewhere or staying in an apartment hotel. I have finally given myself the luxury gift of a home in New York, and boy, does that make life in New York wonderful.

Bankrate: With everything going on in the economy, do you find yourself scaling back?

John Lithgow: It’s all hitting us very quickly, isn’t it? I’m just beginning a job that’s going to take me several months through the theater season. I feel lucky to be employed at the moment, and I just have to hope and trust that people will always need to be entertained, maybe in these terrible days more than ever. They’ll always need actors. You’d think we were dispensable, but we’re not.