When you write for Saturday Night Live you don't have much room for character development, personality nuances, or even jokes that may take more than 10 seconds to make their point. Everything's got to be up front and visible, because you're going on to the next skit right after the commercial break. The new film "Baby Mama" was written and directed by Michael McCullers, who comes from that show, which is the problem with the film.

What's wrong with "Baby Mama" is that it reads like an extended version of a Saturday Night Live sketch, except that it's an hour and a half long. Moreover, it has Tina Fey (the onetime lead writer of Saturday Night Live) as Kate, the lead, in the role of a 37-year-old single woman, vice president of a Whole-Foods-like chain, who now wants a baby but seems not able to carry one because of a problem with her uterus. And the problem with Tina Fey is that she can't find a character within the script, so she stands around waiting for her lines instead of being Kate the character.

Her sidekick, Amy Poehler, who plays Angie, an urban version of trailer trash, is the surrogate mother Kate hires through an insemination agency headed by a totally wasted Sigourney Weaver in a role that could have been played by any actor at all. Poehler has the best lines and at least knows how to deliver them to the inert Tina Fey, but it would take a lot more than one actor to make this movie bearable.

The plot has Kate choosing a sperm donor and giving three eggs to Angie to incubate. But Angie has a bad case of the munchies - as opposed to eating the healthy foods that Kate believes in, and a boyfriend, Carl, who's only interested in the money they'll get. There's also Steve Martin as the very zen president of Kate's company, a role that was obviously written in as a desperate attempt to provide something of an amusing sub-plot.

There's also the scriptwriter's cliche of the all-knowing black doorman of Kate's apartment, and, finally, Kate's love interest, Greg Kinnear, who owns an organic juice store in the neighborhood that Kate finds for her new supermarket. The plot somehow stirs all of these together but emerges with something that tastes as bad as an organic drink of banana, carrot and cabbage juice, which is all I could think of while watching this film.