In his salad days, Aussie director P. J. Hogan specialized in daft, edgy comedies about wildly eccentric characters, people so giddy they’d burst into song when words failed them.

And the world fell in love with Toni Collette’s ABBA obsession in “Muriel’s Wedding,” with Rupert Everett launching into “I Say a Little Prayer” in “My Best Friend’s Wedding.”

Hogan, lately consigned to the likes of “Confessions of a Shopaholic,” takes a stab at recapturing that past with “Mental,” an Australian dramedy built around mental illness and the loony “nanny” who takes it on herself to torment those who torment a mentally ill woman. And if “Mental” it doesn’t quite come off, it’s at least comforting for us and Hogan to see that, to some degree, you can go home again.

“Home” in this case is Dolphin Heads, a little slice of Australian suburbia, probably not far from the Porpoise Spit of “Muriel’s Wedding.”

Shirley Moochmore (Rebecca Gibney) is a nightmare to her neighbors, keeping an unkempt house and a cluster of neurotic and unruly daughters. How does she cope? By singing “The Sound of Music.” All of it.

She could be hanging laundry, and then spin into “The hills are alive…”

“Mom’s gone off again.”

“Gone where?”

“Off her head.”

Shirley “always wanted to be a Von Trapp,” where her kids could “act like a real family.” That way, her absent husband, the mayor (Anthony LaPaglia) would come home. Finally.

As it is, her five girls, often in matching Von Trappist outfits, wear “the disgrace,” and cower every time the chorus to “Edelweiss” comes back around.

The kids – Coral (Lily Sullivan) have taken to self-diagnosis – “I’m pre-psychotic.” “I’m schizophrenic!”

And dad, who long ago moved out, only comes home long enough to quiet things down so he can get re-elected.

But Shirley, bullied by neighbors, her doll-collecting sister and even the mean girl teens at the donut shop, finally snaps and is off to the hospital. Coral, a hormonal teen working in the shark exhibit of a water park, is in no position to run the house. So Dad plucks a 40ish punk chick (Toni Collette) off the street. But they all get more than they bargained from the sassy, blunt and profane Shaz.

Collette vamps through this part as if she was another personality from her TV series, “The United States of Tara” – gum-snapping, insult-hurling and justice administering.

“You’re only as crazy as you let people say you are,” is her motto. Since she has a battered copy of a psychological diagnostic manual as her guide, she sizes up Mom, the kids, the neighbors and others who make Mom manic.

Not all movies that make mental illness cute are Oscar winners, and “Mental” isn’t a noble member of that company. But Coral’s singing, surfing would-be boyfriend, Trout (Sam Clark) is a stitch. Deborah Mailman (“The Sapphires”, my interview with her is here) shows her zany side as an unstable friend of Shaz. And Liev Schreiber hilariously shows up as the sullen shark expert whose expertise was that he’s tough enough and nutty enough to survive a Great White attack (the stuffed shark is the centerpiece of his exhibit). The kids are troubled, but charming.

Alternately touching and seriously silly, “Mental” is good enough to make us want to “Climb Every Mountain,” or at least this one.

MPAA Rating: unrated, with adult subject matter

Cast: Toni Collette, Anthony LaPaglia, Rebecca Gibney, Lily Sullivan, Liev Schreiber,

Credits: Directed and written by P.J. Hogan. An Arclight release.

Running time: 1:54