“I wore shades of gray today in honor of Dexter,” a nattily dressed Michael C. Hall said, referring to the ambivalent nature of his TV character: member of the Miami police department by day, nice guy with a family, serial killer by night.

Settling down into a chair, the star of Showtime’s popular series “Dexter” quipped as he pondered the first question in our interview, “As I pour my water and think of what to say…” In our rambling talk, he gamely discusses myriad topics, from the “toned” bottom of this season’s special guest (John Lithgow), his peculiar tooth brushing ritual, his scary audition experience for a musical (yes, he sings and dances) and life with his wife, actress Jennifer Carpenter, who plays Dexter Morgan’s sister.

Michael also stars in Gerard Butler’s action-thriller, “Gamer.”

You’ve been doing this for several seasons now. How do you keep it fresh? What does John Lithgow bring to the series?

Dexter has evolved in ways that I never anticipated. When we were shooting the pilot episode or even the first season, I never anticipated he would be father to his own child or entertain the idea of actually getting married. So there is built-in evolution and freshness each season.

It’s such a shot in the arm to all of us that we can attract someone of John’s caliber to tell the story with us for a season. He is mind-numbingly chilling and horrifying in this role.

John is a wonderful man, one of the genuinely nicest people I’ve ever met. He is one of the most professional, most technically proficient and yet grounded actors I’ve ever worked with. One of the scariest things I saw and it had to do with my age growing up was John in “The Twilight Zone.” I was scared watching that movie. I was 6 or 7... and probably shouldn’t have been there (laughs). The opportunity to work with him, someone who captivated my imagination in that film, and in so many others—it’s just such a thrill. He has such a sense of play about him, too, which is really infectious.

John’s bare behind makes quite an entrance in the season opener.

John is in his 60s. He has a nice ass (laughs). It’s meaty, taut and toned (laughs). On his first day on the set, John took off all his clothes because that was what the scene called for. He was just so comfortable. I wasn’t in the scene but the crew was remarking on how incredible it was, John Lithgow totally naked, just walking around on the set. He’s just so game.

What is it like working with the babies in “Dexter”?

We had this baby and his sister, who are twins, for the photo shoot. We had two babies hired for the season. Their mother made some unreasonable demands and they went away. Then we had babies for the first and second episode and something happened. They left so we’re on our fourth set of babies now. The babies we have now are phenomenal. All the horror stories you hear about problems with sense of continuity when you’re shooting a scene with babies? Not with these ones. A certain word and these babies will give the same look (laughs). Nothing really grounds you than being able to gaze into the eyes of an infant if you’re in a scene.

It must have something to do with their mother but these babies don’t cry. There was one scene when the baby needed to cry and it was specific. The mother came in before “action” and just thumped him on the bottom of his foot and he cried and cried. We said, “Cut!” and he stopped (laughs) immediately. We call him little baby (Marlon) Brando. He’s incredible. Both of them are. I call them both “he” because they’re playing a boy but they’re actually a boy and girl who are twins.

How do you amuse the babies?

I do know that Zack, the boy, loves it when I go (makes popping sounds with his mouth). That’s my special talent.

What can we look forward to in season four?

What excites me about the fourth season is that Dexter has been evolving. He’s living under the same roof with his wife, her step kids and one child of his own. There’s a movement toward the lighter side of things but that’s balanced with a darkness that the show has yet to explore but exists in this season. The spectrum is broader. That darkness has to do with Dexter becoming entrenched in his relationship with John’s character, the most formidable target he’s ever encountered. It’s probably even more formidable in terms of the effect it’s going to have on Dexter emotionally and psychologically.

Dexter is a serial killer, yet the character has hit a chord with the audience. Do you think that’s kind of weird?

When I read the pilot script and read the book, I thought, how is this going to work? How are people going to identify with this guy? But, I think, the fact that he kills terrible people... all bets would be off. The character is presented through the voice-over element as someone who is telling you as an audience member a secret that he tells no one else. So you’re sort of in on it with him. While his are really big secrets, people can relate to having secrets that they keep or to managing compulsions that they wish they didn’t have. People relish the opportunity to identify with a character who they wouldn’t normally be given that opportunity to identify with and who, on paper, is doing reprehensible things.

People who don’t know that you’ve done musical theater will be surprised to see you dancing and lip-synching in the movie “Gamer” and doing fight scenes as well.

The dance sequence was in the script. That’s how my character entertains his guests, especially if he intends to control them with his mind and kill them. It just seemed like a lot of fun and we came up with the basic soft shoe dance steps. The fact that they chose that Sammy Davis Jr. version (“I’ve Got You Under My Skin”) lent itself to a physicality that found itself to be more of a marionette kind of thing. It seemed really appropriate, considering the string-pulling that the character was doing. So it was a lot of fun doing those scenes, and also the fight scene because it required so much more of an expansive energy than does the stuff I do on “Dexter.”

I’ve worked in musical theater in New York. I played the Emcee in “Cabaret” and Billy Flynn in “Chicago” on Broadway. As far as the fighting goes, I’m glad that at least for a part of the film, I was able to control Gerry Butler with my mind. Otherwise, I might have been in trouble (laughs).

Is there a genre other than musicals that you are interested in?

I sang in a rock band when I was in college (laughs). We weren’t very good, though. We played straight up, blues-based rock.

Can you talk about the serendipity of getting this series and meeting the woman who would become your wife?

You never know where your life is going to take you. When I finished “Six Feet Under,” I moved back to New York, thinking that I would be based there. The “Dexter” script came along and the next thing I knew, I was down in Miami, thinking I was possibly going to move there. But we were going to shoot it here in LA so I’m back in LA. I fell in love with my colleague. It’s remarkable. Four years ago, I didn’t see any of this. I didn’t fantasize about it. It just materialized seemingly out of thin air.

We met at work and we had an immediate affinity for one another as fellow actors and as people. As an actor, what you hope for is to work with people who you trust. We trust one another.

How has your life changed since you got married?

It has changed in that we bought a home that we have decorated and renovated together. It has also changed in the sense of families coming together. She’s from Kentucky; I’m from North Carolina. We had a celebration in Kentucky this past February with all our family members there. That was wonderful.

So do you want to be the father of your own Brando babies someday?

I certainly will be a father one day. I have been surrounded by small babies over the course of my life—small babies as opposed to big babies (laughs). There’s a lot of big babies in this town.

What scares you the most in real life?

An audition that you’re not prepared for. I had to audition for the musical, “The Sweet Smell of Success” that John Lithgow actually did on Broadway. I was in the midst of doing “Cabaret” and I had no voice. I had to sing a very high register song. It was one of those musical auditions where there were 15 people watching you. I completely blew it. I actually bailed out before the big note at the end because I knew I wasn’t going to reach it. Marvin Hamlisch looked at me like I said something horrible about his grandmother or something. It was really bad. That was horrifying.

Dexter’s ritual is collecting blood. What are your own rituals?

We moved to a house on a hill. I usually walk to the top of the hill every morning and back down before I make my breakfast. That’s one ritual. Jennifer noticed the first time she saw me brush my teeth that, after I got the toothbrush clean, I sucked the water out of the toothbrush (laughs). She was like, “Are you doing that to crack me up or do you really do that?” I said, “Yeah, I do that every time I brush my teeth” (laughs).

Does Jennifer now have a say on what you wear?

Jennifer doesn’t tell me what to wear. When I was growing up, there was a time when it was just my mom and me. My mom was not one to lay out my clothes for me or buy my clothes or even iron my shirt. She just showed me how. But Jennifer is certainly there to weigh in. Sometimes I get that (demonstrating a disapproving look). I go, “Really?” or I just change clothes (laughs).

Does Dexter seep into your dreams?

I don’t really dream as Dexter, though there have been some dreams where elements of Dexter have crept in. I did have one dream where Little Chino, the giant guy from the second season who my character had trouble killing, kept showing up at my door and I was me. I was like, “Why are you here?” I would get him to leave and I’d go to the refrigerator. The door would ring again and he would be there again. I’m sure this conversation I’m having with you right now will affect my dreams (laughs). There was this guy asking me questions...