Mills, who also wrote and directed Beginners and 20th Century Women, says his films all ask, "What are you going to remember? Who are you going to remember it with or what are you forgetting?"

Transcript

A MARTINEZ, HOST:

In the new film, "C'mon C'mon," Joaquin Phoenix plays a radio journalist named Johnny.

(SOUNDBITE OF FILM, "C'MON C'MON")

JOAQUIN PHOENIX: (As Johnny) When you think about the future, how do you imagine it'll be? What will stay with you? And what will you forget?

(SOUNDBITE OF CHILD GIGGLING)

MARTINEZ: Johnny asks some of life's big questions while taking care of his nephew Jesse. NPR's Mandalit del Barco met up with Mike Mills, who wrote and directed the film inspired by his relationship with his child.

MANDALIT DEL BARCO, BYLINE: I was already wearing headphones and had my recorder rolling long before approaching Mike Mills and his dog Mickey.

(SOUNDBITE OF DOG BARKING)

MIKE MILLS: It's OK.

DEL BARCO: Hi.

MILLS: Hi.

DEL BARCO: They greeted me outside the LA bungalow the filmmaker uses as his studio. Inside, I tell him "C'mon C'mon" is the most public radio movie ever.

Even just the details of, like, you always have to wear your headphones. You have to point this mic at the right place.

MILLS: Yeah.

DEL BARCO: And I mean, I don't know if you noticed, but I always start the recording as I'm coming...

MILLS: Yeah. I knew what you were doing.

(LAUGHTER)

DEL BARCO: That's because Mills is a big public radio listener, especially of shows like This American Life, hosted by Ira Glass.

MILLS: So I look at, like, Ira Glass' life. I'm like, that seems genius. And Ira's had such an influence on me and my films and my writing, so I've been, like, a fan forever.

DEL BARCO: Mills even talks a bit like Ira Glass. For his film, he consulted with a producer who's worked for Ira's show, Starlee Kine.

MILLS: There's a great line in the movie that's really from Starlee. The kid - Jesse's recording the sounds of the train going across the Manhattan Bridge, which is this tremendous sound, right? And Joaquin says, you know, you're recording this banal thing, but you're, like, keeping it forever; you're, like, making it immoral (ph). That whole idea was something that Starlee said is why she loves to record stuff, is you kind of get to hold on to it in our incredibly ephemeral world. You get to grab on a little bit.

DEL BARCO: Mills also cast Molly Webster, senior correspondent for WNYC's Radiolab, to play the part of a radio journalist working with Joaquin Phoenix's character. Webster says Mills was open to collaboration.

MOLLY WEBSTER: He, me and Joaquin just, like, really talked through who were we as journalists? What were we hoping to accomplish? Like, he just was so interested in really nailing and truly representing, like, the craft of radio journalism.

DEL BARCO: For the film, Molly Webster and Joaquin Phoenix interviewed real kids around the country about life.

(SOUNDBITE OF FILM, "C'MON C'MON")

PHOENIX: (As Johnny) If you could change one thing about yourself, what would it be?

UNIDENTIFIED ACTOR #1: (As character) My attitude.

PHOENIX: (As Johnny, laughter) What's wrong with your attitude? You seem like you have a great attitude.

(As Johnny) What would you change about yourself?

UNIDENTIFIED ACTOR #2: (As character) My anger.

PHOENIX: (As Johnny) If you could have any superpower, what would it be?

UNIDENTIFIED ACTOR #3: (As character) The ability to bend space and time.

(LAUGHTER)

DEL BARCO: Throughout "C'mon C'mon," those interviews are interwoven with the fictional story Mills based on his close relationship with his child Hopper.

MILLS: There's some very Hopper moments or things that Hopper did or said. But it's also an abstraction from that inspiration or from that sort of gooey heart. There's something so intimate - like, talking with my kid while giving them a bath, talking with my kid about something that happened at school while we're trying to go to sleep.

DEL BARCO: In one scene, Johnny tears up while reading the book "Star Child" to Jesse.

(SOUNDBITE OF FILM, "C'MON C'MON")

WOODY NORMAN: (As Jesse) You're crying.

PHOENIX: (As Johnny) No, I'm not.

NORMAN: (As Jesse) Yes, you are. You're definitely crying. See? You're crying.

PHOENIX: (As Johnny) I'm not. It's just it's true. You forget everything.

NORMAN: (As Jesse) No, I don't. You do. You're stupid.

PHOENIX: (As Johnny) Yeah. You'll barely remember this. You'll have, like, a few blurry memories.

NORMAN: (As Jesse) That's very stupid. You're just the stupidest stupid person.

PHOENIX: (As Johnny, laughter).

DEL BARCO: Mills, who's married to fellow filmmaker Miranda July, says he tried to capture the kind of intimate, infuriating, silly and poignant moments he's experienced as a father.

MILLS: If you're a parent, you're constantly, like, grieving the end of these different versions of your kid. Like, the kid you knew a month ago is always sort of disappearing. And I feel like they kind of accelerate your own experience of your time on Earth as a parent, too.

GABY HOFFMANN: Mike is an incredibly sensitive, thoughtful, interested, very smart, perceptive person.

DEL BARCO: Actress Gaby Hoffman plays Johnny's sister and Jesse's mother in the film.

HOFFMANN: It gets at so much of what is the essence of parenthood and its beauty and complexity and challenge. I feel, when I watch the movie, so grateful because I don't see many films made these days that are actually about life, the actual experience of what it is to be alive in this world, in this country right now.

DEL BARCO: Mills' films are also about who he is and was. He was born in Berkeley and grew up in Santa Barbara, where as a teen, he skateboarded and played in punk rock bands.

MILLS: I continued to be such a wannabe musician. Like, I work with musicians all the time. I idolize them. Or - I just find, like, their art form is more tapped into magic than mine. And I'm always trying to get mine to be like music.

(SOUNDBITE OF AIR'S "MIKE MILLS")

DEL BARCO: In the 1980s, Mills was a graphic artist who made music videos - among his clients, the Beastie Boys, Sonic Youth and Air, who named a song after him.

(SOUNDBITE OF AIR'S "MIKE MILLS")

MILLS: When I was in my 20s, 30s in New York City, I met a whole community of skate artists, which is a lot of how I got into the film world. Weirdly, that's how I met Spike Jonze. That's how I met so many people that are in my film upbringing.

DEL BARCO: He was also brought up by his nonconformist mother, who had wanted to be an architect and a World War II pilot.

MILLS: Hard-drinking, hard-smoking, short-haired, pant-wearing, sort of Humphrey Bogart-vibed person - that's Mom. And Mom had me when she was 40 in 1966, very unusual.

DEL BARCO: In 2016, he wrote and directed a film loosely based on his relationship with his mom. Annette Bening plays her in "20th Century Women."

(SOUNDBITE OF FILM, "20TH CENTURY WOMEN")

ANNETTE BENING: (As Dorothea Fields) No, I don't - I just think that, you know, having your heart broken is a tremendous way to learn about the world.

DEL BARCO: Mills also wrote and directed a film loosely based on his relationship with his father.

MILLS: My dad came out of the closet when he was 75, after my mom passed away. And I started writing that really quickly after he died. So that film has a lot of just, like, direct memory.

DEL BARCO: Ewan McGregor plays Mills, and Christopher Plummer plays his dad in the 2010 film "Beginners."

(SOUNDBITE OF FILM, "BEGINNERS")

CHRISTOPHER PLUMMER: (As Hal Fields) I'm gay.

EWAN MCGREGOR: (As Oliver Fields) I remember him wearing a purple sweater when he told me this, but actually, he wore a robe.

PLUMMER: (As Hal) I'm gay.

DEL BARCO: The idea of memory comes up in all his movies.

MILLS: Like, what are you going to remember? Who are you going to remember it with? Or what are you forgetting? Or what are you getting wrong?

DEL BARCO: Mills filmed "C'mon C'mon" in black and white so it does feel like a shared memory.

MILLS: Most of my films, most of my writing needs to start with someone I know, someone I can observe and someone who I love or someone also like - I'm trying to figure them out (laughter).

DEL BARCO: Mike Mills says he makes films about the people he loves to capture their essence forever.

Mandalit del Barco, NPR News.

(SOUNDBITE OF BRYCE DESSNER AND AARON DESSNER'S "HERE THEY ALL COME") Transcript provided by NPR, Copyright NPR.