Dysfunctional-family fireworks light up Cherie Nowlan and Keith Thompson's dark comedy about (s)mother love and the irresistible lure of the spotlight. Up-and-coming stand-up comic Jean Dwight (Brenda Blethyn) was carving her niche as a protofeminist comedienne, a sort of English Phyllis Diller with a scorched-earth line in man-bashing. But after marrying Australian rocker John (Frankie J. Holden), whose one-hit career peaked with a cover of Tina Turner's "Nutbush City Limits," and moving with him to Sydney, Jeannie's ambitions were put on hold. Two children and a divorce later, she works days at a cafeteria and plays bottom-of-the-barrel venues at night, doing her best to live up to her billing as "the raunchiest housewife in clubland" by ragging on menstruation, menopause and men. On stage and off, Jean is volatile, thin-skinned, sharp-tongued and supremely self-centered. She's lively company, especially after a few drinks, but frighteningly quick to turn her seething discontents on her grown sons, dutiful Tim (Khan Chittenden) and brain-damaged Mark (Richard Wilson), who are no match for her self-pitying theatrics and guilt-inducing outbursts. Jean relies on Tim — whose small moving business is entirely dependent on the van she helped finance — to ferry her to and from gigs, while she babies Mark by using his disability as an excuse to keep him docile and dependent. Tim finally works up the nerve to defy her by dating pretty, outgoing Jill (Emma Booth), and Jeannie responds to the shift in the balance of power with every ounce of sarcasm, condescension and cruelly belittling humor she can muster. Feel-good ending notwithstanding, this Australian comedy is one pratfall away from sheer, unrelenting tragedy: Jean is a self-deluded monster and her sons are a couple of traumas away from being emotionally crippled for life. That said, it is funny, in the same queasy way as MURIEL'S WEDDING (1994), and shot with the same sympathy for the underdog — who in this case happens to be Jean. It's a mistake to think the film's center is sweet Tim's coming-of-age: His gradual emergence from Jean's long shadow is just a sidebar to her painful realization that her good-time-gal act is just that — and a shopworn one in desperate need of a rewrite. Uneven and sometimes grating — Wilson's Mark is an irritating mix of tics and wise-child quips — the film is as sloppy, loud and sentimental as Jean herself.