I'm slightly mistrustful of titles that include exclamation points. They always remind me of the musical version of The Elephant Man, Elephant!, in The Tall Guy ("... there's an angel with big eeears..."). But in the case of Mamma Mia!, I'm actually surprised the title only included one exclamation point -- you can imagine the filmmakers or the creators of the stage version embracing even more emphatic punctuation, just to let you know that This! Is a Musical! And also Wacky!! As if chorus lines of men in flippers, Meryl Streep waving a feather boa, and enough ABBA music to sate the leads of Priscilla, Queen of the Desert wouldn't have clued you in.

The movie, like the stage musical it's adapted from, is essentially and unabashedly an extended gimmick -- an excuse to sing and perform songs that originated from the Swedish musical group ABBA. Characters spontaneously burst into song not because they're aspiring performers (Chicago), or because their singing is meant as a melodious soliloquy (Sweeney Todd), but because the situation or their emotional state reminds them of an ABBA song (sometimes more tangentially than others), and they decide to share it with everyone. I've had friends like this in real life, although that seems to have been a college-age thing.

How much you like this movie depends not only on how much you like ABBA, but how much you can enjoy the joyous artificiality of this musical. Reality is stranded somewhere else. Mamma Mia! is set on a breathtakingly gorgeous Greek island, on the day before 20-year-old Sophie (Amanda Seyfried) will get married. Sophie's mother Donna (Streep) has never revealed the identity of Sophie's dad, but the girl has narrowed it down to three possible contenders: Harry (Colin Firth), Bill (Stellan Skarsgard) and Sam (Pierce Brosnan). She secretly invites them all to her wedding, hoping her mother won't find out. But Donna isn't easy to fool, and neither are her best friends in for the wedding, Tanya (Christine Baranski) and Rosie (Julie Walters). You can see the potential for all kinds of comedy mix-ups, not to mention a smorgasbord of ABBA tunes.

The movie often careens around cheerfully like a kid turning cartwheels: "Look at me, I'm a funny movie, with lots of female bonding and very catchy musical numbers! Hey, now I'm being campy, didn't you love those dresses in "Money, Money, Money"? Can you believe we managed to work 'Chiquitita' in here? You'll never guess what's next!" At other times, the musical numbers go on a little too long -- I understand that "Voulez Vous" was supposed to represent a dark bacchanalia as well as a vortex of confusion for Sophie, but it never sucked me into a sense of decadence and even dragged after awhile (maybe because I didn't know the words and couldn't sing along to that one).

As with last year's Hairspray, the older characters were more fun for me to watch than the younger generation. Sophie and her betrothed are so cute and sweet they practically blend in with the scenery, and Sophie's best friends are almost interchangeable. Compare her friends to Donna's -- the minute you see Walters and Baranski onscreen, you start to laugh, and they only improve from there. Baranski's big number, "Does Your Mother Know," recalls Jane Russell in Gentlemen Prefer Blondes, belting out "Anyone Here for Love" in a gym full of Olympic studs, and provides a huge kick when Mamma Mia! threatens to lose its exclamation point in the silly storyline. Walters is zany without being annoying, and Firth does his standard Colin Firth-y thing (yes, the shirt comes off, in case you were wondering).

But it's Meryl Streep who grabs the movie by the tail and shakes it, belting out songs like there's no tomorrow, and keeping the energy pumping. I especially loved the early scenes where she marches around in overalls and a tool belt, as well as the scenes where she dons over-the-top crazy costumes. Her weakest moment was the one probably intended as her biggest number: "The Winner Takes It All," in which she looks almost haggard and her outfit oddly unflattering. The sequence might have been a Broadway show-stopper, but it 's too long for a movie -- it reminds us that the the storyline was shoehorned around existing songs that might not fit the story's situation as well as a tailor-made score might.

Streep is one of the stronger singers in Mamma Mia!, although the younger cast all have sweet voices that never waver out of tune. Firth's singing voice is slightly higher-pitched voice than you might expect, but it's still charming. Skarsgard seems to be avoiding solos as much as possible, and the result is not at all bad. And then there's Pierce Brosnan, who tries his very best while muddling through at least two songs. He would have been excellently cast if he only didn't have to sing. It's too bad they couldn't have found a way for him to talk through the songs like Rex Harrison, or looped the singing, because the audience had an unfortunate tendency to giggle at his vain attempts at musicality.

Mamma Mia! is a strange cinematic treat -- surreal, bouncy, occasionally downright cheesy, and if you know your ABBA songs, fun to sing along with, as much of the audience did during the preview screening I attended. Sing-along versions of this will surely be popular for ages to come. The movie is so infectiously bubbly overall that it's difficult to carp about voice talent and uneven pacing and the surprisingly drab outfits the characters plan to wear to the wedding (especially compared with such fabulous fashion everywhere else in the film). It's a good movie to watch with a bunch of lively friends. Make sure you stay through the first half of the credits at least, or you'll miss one of the best over-the-top numbers in the entire movie, as well as more eye-popping costumes.