"Bridesmaids" is an improbable movie for numerous reasons.

We just entered the blockbuster season, yet here’s a 2D women’s comedy featuring no special effects. It’s sandwiched between last week’s "Thor" and next week’s "Pirates of the Caribbean: On Stranger Tides." Which of these things is not like the other?

"Sex and the City" and its sequel are the only women’s comedies to open during summer in recent years. But "Bridesmaids" offers none of the hedonistic escapism of SATC. These women have problems to which we middle classers can actually relate.

That last quality has become improbable for Hollywood, regardless of genre.

These are also real-looking women. The cast are all beautiful in various ways, but with the exception of Rose Byrne, whose physical perfection factors into the story, it’s all attainable beauty. These women look and act their age. The producers, bless them, didn’t throw in the obligatory 20-year old character just to provide eye candy. Improbable.

This is a raunchy comedy produced by Judd Apatow, yet its target demographic is female. I doubt anyone would consider Apatow’s oeuvre ("40-Year Old Virgin," "Knocked Up") femme-friendly. Again, improbable.

Finally, "Bridesmaids" avoids tearful melodrama, dancing around tables, Motown music and most of the clichés of its genre. Which helps make it the rare women’s movie that doesn’t condescend to its audience. The movie takes its audience into the gutter in many ways, but it never talks down to them.

For these reasons and more, "Bridesmaids" works. It has more than its share of flaws, but it’s a hilarious movie with a heart in exactly the right place.

Both the heart and the funny begin with Kristen Wiig playing Annie, whose life is a hopeless wreck. The ensemble cast is big and talented, but Wiig grounds everything with the most diverse, strongest role of her career.

Annie recently suffered a failed bakery business that has left her destitute. Her only "romance" comes from being used for booty calls by a handsome but demeaning cad (Jon Hamm). She is working at a jewelry store to pay the rent on a room she hates. Her car is falling apart and has no taillights.

So when her best friend Lillian (Maya Rudolph) announces her engagement and asks Annie to be her maid of honor, Annie has to dig deep to act excited. She feels envious of her friend and has no way to pay for the things a maid of honor is supposed to do.

Enter Helen (Rose Byrne), Lillian’s wealthy, perfectionistic new best friend, who challenges Annie during each step of planning and consistently steals (or buys) Lillian’s affection away from Annie. Watching Wiig and Byrne spar passive aggressively is great fun.

But not nearly as much fun as watching Melissa McCarthy steal scene after scene. She plays Megan, the groom’s sister, who takes uncouth to unprecedented depths for a female character. McCarthy gives a fearless, breakout performance, and her character develops in ways you will not expect.

Wendi McLendon-Covey and Ellie Kemper lend laughs as the other bridesmaids, and Chris O-Dowd as Annie’s love interest is going to earn a lot of attention.

This is also Jill Clayburgh’s final role. She died too young, but I’ll wager she’d be proud that this was her last film.

I’m certain of two things. First, you will laugh at "Bridesmaids." Second, you will wish the filmmakers had cut at least one scene. Most of the dialogue was improvised and doesn’t always work, and the movie indulges in toilet humor too much. But I’ll confess: I laughed in spite of myself even at the scenes that probably could have been edited out.

What isn’t so certain is how "Bridesmaids" will perform. All those improbabilities make this a hard movie to predict.

Women, are you ready for a raunch-com of your own? Men, will you pay for a movie starring women almost exclusively?

I think you’ll both be happy if your answer is yes.