The dazzling poster for "Mamma Mia!" boasts the glowing portrait of a young and sprightly Amanda Seyfried, who you might know as the dumb one from "Mean Girls." But this energy boost of a musical is not about the young and the beautiful-if anything, "Mamma Mia!" belongs to the older, seasoned ladies of the cast who eagerly own their roles and aging voices, rendering most of their young and sprightly co-stars utterly forgettable.

Fortunately, Amanda Seyfried is not one of the unremarkable twentysomethings. We already know she's more than just the "dumb one"; after all, she starred in "Alpha Dog" and "Big Love." In "Mamma Mia!" we find out she can sing. Seyfried is genuine and lovely as Sophie, a bubbly bride-to-be who longs for a father she never knew. Her mother, Donna (Meryl Streep), is a former pop sensation running a hotel on a Greek island. It's Sophie's impending marriage that prompts her to seek out her father-or rather, her three possible fathers: Harry, Bill and Sam (played by Colin Firth, Stellan Skarsgard, Pierce Brosnan and his pitiful vocal stylings). Comedy, nostalgia and spontaneous musical numbers ensue.

The plot is barely there compared to the ABBA hits that get cranked out every five seconds, but by now we know we can't expect much from a script whose sole purpose is to accommodate the lyrics of a European pop sensation. Director Phyllida Lloyd and screenwriter Catherine Johnson also held similar roles for the madly popular theater production, and the result is an island paradise that appears lit by hot stage lights. They play up the island's pearly white plaster village and sparkling waters with a smidgen of glittery '70s camp, and the fantastical touch makes the thin plot much more aesthetically pleasing.

If it weren't for ABBA's penchant for catchy hooks and the all-star casting of Donna and her retired back-up singers, "Mamma Mia!" would be nothing but a bad story. These divas make it bearable-belting lyrics as if they're Broadway superstars. They're not. Well, except for Christine Baranski, who shines as the sexy, thrice-divorced Tanya. The ever-youthful Baranski has a tendency to mercilessly steal scenes from her less musically-inclined co-stars, as she demonstrated with Richard Gere in "Chicago." Rosie-the hysterical Julie Walters, taking time off from being Mrs. Weasley-is not much of a sensual siren, but her pseudo-seductive "Take a Chance On Me" is comic gold. As for Meryl Streep, don't believe the hype. She's not that great of a singer. Her voice often falters, but not enough to detract from her portrayal of a once-vibrant mother who misses young love as much as her daughter longs for a father.

If you need one reason to see this movie, see it for the scene in which Donna, Tanya and Rosie lead the ubiquitous island natives to the dock for a vivacious rendition of "Dancing Queen." It is these ladies' exuberant star power alone that transforms this mediocre movie compilation of ABBA songs into a delightful portrait of letting loose and living it up in your fabulous 50s. Actually, the whole film seems to speak to an older generation entirely: baby boomers, hippies and the like. At least, they were the ones who declared a dance party in the aisles once the credits hit (we also heard rumor of a party at the Castro's Badlands following the screening). Like ABBA, they're refusing to get old. And perhaps that's the underlying point of "Mamma Mia!"-to celebrate the careless nature of being young at heart, no matter how old you might be.