It might go unnoticed by some, but there’s some impressive girl power on display in "Baby Mama" - and also the funniest Steve Martin performance in a decade.

Unlike so many male-oriented comedies that use women as one-dimensional props, "Baby Mama" is about two strong, funny women running the show. And it’s instead the movie’s most prominent male, an affable Greg Kinnear, who is relegated to the part of sweet and sensitive romantic interest.

Kate (Tina Fey) is a go-go working woman, a rising executive within Barry’s (Steve Martin) corporate empire. Barry is the kind of granola-cruncher who sits barefoot on top of the conference table, hands pressing against his temples as he ponders his latest business venture: An organic, environmentally friendly grocery store, which is to be built in an up-and-coming area of Philadelphia.

As Kate sets out to work on the new project, she also sets out to become a mother. Told by a doctor that she’s statistically infertile, she decides to hand over $10,000 to a surrogate - a woman who can be injected with Kate’s eggs and then carry Kate’s baby to term. That "baby mama" ends up being Angie (Amy Poehler), a blue-collar woman who’s a bit flighty and naive, and more than up-front about the fact that she’s only doing this for the money.

There isn’t just one storyline going for chuckles in "Baby Mama," but three. As Angie ditches her "commonlaw husband" and moves in temporarily with Kate, there’s the humor of two polar opposites occupying the same space. Kate works all day while Angie stays home, playing video games. When Kate complains about not meeting any men, Angie drags her out to an all-night dance club.

Yet it’s not just an "Odd Couple" comedy about cohabitation, but also a comedy about socioeconomics. Stepping out of the car during one of their first visits, Angie offers to pay for gas, but it’s clear as she pretends to check her pockets, that she has no intention of chipping in. Kate is rich, Angie is poor, and a good number of the movie’s punch lines stem from the fact that Kate eats organic while Angie eats fast food.

But foremost - as if Fey’s recent appearance on the cover of Entertainment Weekly wasn’t enough evidence - this is a star vehicle for two new major movie talents, two up-and-comers who are using "Baby Mama" to officially announce their arrival. Both Fey ("30 Rock") and Poehler have already come to the nation’s attention through "Saturday Night Live," but in this setting, they bounce off each other in ways that are both affectionate and sassy, suggesting a wider range of emotions than some might be expecting.

Their chemistry helps to keep "Baby Mama" moving at a fast clip, but it’s also the supporting players who fill the film with surprises. Not only does Martin steal scenes as the tree-hugging boss, but John Hodgman (from the Apple ads) shows up as an overconfident doctor, and Sigourney Weaver holds her own as the owner and operator of the surrogate agency.

The film is generous in the way it doles out the punch lines, and smart in the way it makes the comedy about the characters, and not the bodily functions. Boiling it down, "Baby Mama’s" essentially a movie about people coming together who would never otherwise meet, a series of unexpected crises and joys that ultimately make these strangers into better people. For anyone frustrated with the ever-expanding catalogue of shock comedies, it might just be the surprise of the spring.