Sometimes the side dishes are tastier than the entree, in comedy as well as cuisine, which is the case with "Baby Mama."

The main course is a souffle involving Tina Fey, whose eggs are rising in another woman's oven while she herself has been rising as a corporate star. She's Kate Holbrook, VP/development of the wildly successful Round Earth organic food chain.

Single and late-thirtysomething, Kate has always prioritized career above private life but now hears the thunderous ticking of the bio-clock and decides to have a kid on her own. Trouble is, the doctors say she's got only a one-in-a-million chance of getting pregnant, so she must outsource the actual baby-birthin' itself to a surrogate mother -- her Poehler opposite.

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'Baby Mama'

3 stars = Good
Ratings explained

• Starring: Tina Fey, Amy Poehler, Greg Kinnear, Steve Martin.
• Rating: PG-13 for crude and sexual humor language and a drug reference.
• Web site:babymamamovie.net

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That would be Angie Ostrowiski (Amy Poehler), a gum-chewing South Philly working girl, whom some -- including Kate -- would consider trailer trash. But once the papers are signed and the fertilized egg implanted, they're stuck with each other. More so, when Angie's redneck boyfriend kicks her out and she shows up at Kate's door needing a place to live.

Most of "Baby Mama's" yuks derive from the resulting tried-and-true "Odd Couple" irritable cohabitation situation. Uptight, sophisticated Kate reads every child-care book she can lay her hands on, baby-proofs the entire apartment, buys state-of-the-art equipment (a stroller with airbags), researches the best preschools. Angie can't get the child-proof lock off the toilet-seat lid, sticks her gum under the antique coffee table and constantly bickers with her hostess in between home-karaoke demos. Kate's efforts to turn free-spirited Angie into a yuppie-correct pregnant mom are doomed to fail.

Poehler can get on your nerves. Fey plays it straighter, and very well, as a kinder, gentler (but still bossy and controlling) Julia Louis-Dreyfus. The gals' two guys -- Kate's juice-bar owner Greg Kinnear and Angie's Neanderthal Dax Shepard -- do their predictable thing. .....

There are a few very funny scenes, notably at the Surrogacy Center's group therapy sessions, where one guy says, "The wife and I are Methodists. Ashley here [another surrogate mom] is a Wiccan."

Ah, but it's those delicious side dishes that are wonderful. First of them is Sigourney Weaver as the Surrogacy Center head, such a terrific (and ironic) role model that she is still constantly churning out other women's kids in her late 50s.

The second is nebby, opinionated Oscar (Romany Malco), the hilarious, all-hearing, all-seeing doorman. He's the precise equivalent of what, in a bygone racial era, would've been the sassy maid played by Hattie McDaniel.

But best of all is Steve Martin as Kate's boss, the ultimate New Age entrepreneur-guru-founder of Round Earth foods (appropriately named Barry), complete with long silver ponytail and a habit of intimate forehead-touching. "I love it, Kate!" he says at one point. "I want to reward you with five minutes of uninterrupted eye contact." Martin plays him as a mutant hybrid of L. Ron Hubbard and Bill Gates, ever eager to share the inspirational wisdom of his experiences ("I've toasted pine nuts on the edge of an active volcano."). Martin alone is worth the price of admission.

Fey, who wrote the script for her own "Mean Girls" (2004), did not do so here. Credit goes to writer and first-time director Michael McCullers, co-scenarist of the two "Austin Powers" sequels, who previously worked with Fey, Poehler and producer Lorne Michaels on "Saturday Night Live" years ago.

"Baby Mama," not surprisingly, has the feel of an expanded "SNL" reunion sketch. All serious issues handily evaporate with the sappy-happy ending. But who would come with serious expectations?

In music, there's "easy listenin'." In film, there's "easy watchin' " in general -- here, in particular.