Toni Collette as Shaz (Dada Films)

Australian director P.J. Hogan reunites with Toni Collette in a knockout comedy that cuts to emotional truths but still ends with a fart joke—and it’s a good one.

It’s as though the despondent family at the heart of Hogan and Collette’s 1994 hit Muriel’s Wedding was flipped inside out. The same dynamics are here: a negligent husband has driven a suburban Australian mother past her tipping point, and their children have become emotionally crippled. Except now Collette’s character is not a shy girl running away from her life, she is saving everyone else’s.

Shirley Moochmore (the excellent Rebecca Gibney) has wanted her life to be The Sound of Music since girlhood. But the Moochmores are not the von Trapps. They are mocked for not reaching the superficial standards of their suburban neighbors. Shirley’s lawn is littered with trash, her husband is an adulterer, and her five daughters all believe themselves to be psychotic losers.

So Shaz (Collette) is hired to take care of the kids while Shirley sleeps off insanity in a mental hospital. A chain-smoking Julie Andrews with a pit bull, Shaz takes everyone to task for letting other people run their lives into the ground—children, husband, and neighbors included. It’s always a pleasure to see Collette in a role with top billing, and Shaz is so gloriously over-the-top that she fills the screen.

The plot is ludicrous but the emotions feel accurate. Hogan’s script is rambunctious—lines either cut to the heart of how a character feels, or they’re just cutting. There is something absolutely Australian about the film’s crass humor and even-handed barbs. Phrases like “Fuck a dolphin” just need an Australian accent to work correctly.

In a memorable sequence, Shaz shares her insanity philosophy with the Moochmore kids, explaining Australia’s history as a British mental asylum for deported lunatics, who then inbred over the years. “We’re nothing but a living experiment in madness under constant observation by the psychiatric community of the world,” she says. The kids protest by pointing to Kylie Minogue as an example of a normal person, and Shaz says that’s exactly why Minogue, Nicole Kidman, and Rupert Murdoch got to leave. When two bullies then show up to mock the Moochmore kids, Shaz uses a psychiatry textbook to physically beat them up. This is how she begins to teach the kids how to get over their problems and avoid the asylum.

The story’s structure is predictable. Will the kids turn out alright? Can Shirley be saved? Is there more to Shaz than there seems? Will the Moochmore patriarch sing “Edelweiss” in the finale? (Guess.) But there are dozens of exuberant moments and perfect one-liners before you get to the end, and that’s the film’s real strength.