Baby Mama delivers the laughs non-stop. The story focuses on 37-year-old single business executive Kate Holbrook (Tina Fey) who suddenly finds herself with strong maternal yearnings. But she is told she has only a million in one chance to conceive disheartening news that sends her straight to a surrogacy agency whose pretentious owner (Sigourney Weaver) hooks her up with Angie (Amy Poehler) a low-rent working girl with a loser husband (Dax Shepard) who has decided she should become a surrogate as part of a get rich quick scheme. When Kate learns the Angie is indeed pregnant she starts preparing for the blessed arrival. But much to her chagrin what she doesn’t is expect is for Angie to land on her doorstep saying she has nowhere else to go. This sets up a female version of The Odd Couple as Angie’s trailer trash lifestyle clashes repeatedly with Kate’s ordered existence. Despite the differences the unlikely pair learn to accept each other and strike up a tentative friendship all in the name of baby-to-be. Considering the fact that Fey and Poehler worked together on Saturday Night Live and developed unique comic timing as anchors of “Weekend Update ” the chemistry they exhibit here in their first on-screen teaming should not come as a surprise. They are absolutely hilarious together as the screen’s latest--and greatest--Odd Couple (OK next to the originals Walter Matthau and Jack Lemmon). Fey in particular has a nice Mary Tyler Moore quality to her grounding her comedy in reality and creating an extremely likeable presence either on the big screen or small as she proves weekly in 30 Rock. Surrounding the two leads is a swell cast of comic vets led by Weaver a riot as the 50-something baby-obsessed surrogate agency head who likes to remind her clients that she is still fertile. Offering nifty support on the male side are Greg Kinnear as a nice lawyer-turned-juice bar owner Kate develops an attraction to; Romany Malco as the apartment doorman who likes to commiserate with the tenants; and Shepard as Poehler’s n’er do well common law husband. Steve Martin also shows up for an amusing turn as Kate’s boss--a silver hair pony tailed new age owner of a chain of organic food markets. For what is essentially a chick flick it’s a bit surprising to learn it was written and directed by a man Michael McCullers who acquits himself nicely in his feature debut behind the camera. Some of that may be due to the fact he too is a SNL writing alum and speaks the same kind of improvisational language as his stars. As co-screenwriter of the Austin Powers films with another SNL grad Mike Myers McCullers clearly knows a thing or two about screen comedy. His experience shows in his effective and easy-going work on Baby Mama which despite constant contemporary references feels in some way like a throwback to the more genteel movie comedies of the ‘50s and ’60--right down to the peppy musical score and bright technicolored look of the film. Key for making his vision work is in casting. When you’ve got pros like these working for you what could possibly go wrong?