'C'mon C'mon' finds Joaquin Phoenix pivoting from 'Joker' to his sweet side

Joaquin Phoenix does not slaughter anyone or go on any riot-inciting rants in "C'mon C'mon." In a major switcheroo from his Oscar-winning previous film "Joker," he leans into the sweetly befuddled side that characterized his early work in movies such as "To Die For."

Phoenix plays an Ira Glass-like radio journalist named Johnny. He and some colleagues are working on a story that involves interviewing immigrant children about their notions of the future when he gets a call from his sister (Gaby Hoffman), asking him to care for her son Jesse (Woody Norman) while she helps her ailing ex-husband. What follows is a look at how impossible it is to do a job that somehow billions of people do, anyway: be a parent.

Although its dramatic black-and-white images set it apart, "C'mon" is not an unfamiliar story. You've probably seen plenty of versions of the one about a half-formed adult who is supposedly taking care of a precocious kid but who gradually realizes the kid is taking care of him. What sets "C'mon" apart are the performances and the care with which writer/director Mike Mills ("Beginners," "20th Century Women") lingers over the thorny details of suddenly being a de facto dad to a kid who thinks it's fun to disappear in grocery store aisles or lock himself in public bathrooms.

As American Jesse, the British Norman is simply astonishing. He's playing one of those kids who is startlingly wiser than his years, a character that can easily make one's screen-punching reflex kick in, but he's so alive and spontaneous that you never catch him slipping into a "cute kid" act. His best moment, in fact, may be a wicked look that's barely captured as it flashes across his eyes when he's teasing his uncle at bedtime. Great child performances only happen when the child and director are both excellent and, however he did it, Mills managed to capture one beautiful, real, telling moment after another from Norman.

His acting partners aren't bad, either. Hoffman's role is impossible — she's basically Perfect Mom — but you believe in it because of her intelligence and forthrightness. That's even true when her character basically becomes the movie's thesis statement: "Nobody knows what they're doing with kids. You just have to keep doing it."

"C'mon C'mon" is a little too tied to Hallmark Store plaques like that one and a little too unaware of its characters' privilege (all of them are in a position to drop their work at a moment's notice). But, whenever a scene gets phony or self-righteous, Norman pulls it back with his devilish humor, like when his uncle is trying to role-play as part of his favorite, made-up game about being an orphan. It's fun for us to watch a good actor like Phoenix be a bad actor but it's not fun for Norman's Jesse, who cracks, "You are just terrible at this."

Johnny starts to get better at it, under his nephew's tutelage. And, although nothing major changes over the course of two hours, he also gets better at being a person. Because his sister's advice applies to the difficult job of being a human, too: Nobody knows what they're doing. You just keep doing it.

'C'mon C'mon'

*** out of 4 stars

Rated: R for language.

Where: In limited theaters.