Baby Mama 

Not many people can claim to have single-handedly originated an entire movie genre, but Lorne Michaels has done exactly that. Over his decades of producing “Saturday Night Live,” Michaels has been responsible for spinning off countless popular characters on the big screen, in the process creating a generally reviled film form known as “The Extended SNL Sketch.” Shining examples include Coneheads, It’s Pat!, A Night at the Roxbury and The Ladies Man. Every once in a while, the formula works — The Blues Brothers and Wayne’s World would be cases in point. This isn’t one of those times.

Baby Mama isn’t based on “SNL” characters, of course, but I include it in the same tradition because Michaels produced the film, a number of the show’s alumni make cameo appearances, and it’s predicated on the chemistry Tina Fey and Amy Poehler perfected as castmates over six seasons. Fey plays Kate Holbrook, a vice president at an organic food company who is 37, single and suddenly overcome by the desire to raise a child. We’re never given a credible explanation for this, though we do soon learn that her chances of conceiving are one in a million. She immediately nixes the idea of adoption. The reason we’re offered is that the process would take too long. The truth is simply that it has less comic potential than the option of surrogacy.

Not a lot less, though, as it turns out. Kate contracts with a pricey agency operated by Sigourney Weaver, and, faster than you can say The Odd Couple, she’s confronted with the woman whose uterus she’ll be leasing for the next nine months. Poehler costars in the role of Angie Ostrowiski, a low-class South Philly ditz who’s just left her white trash common-law husband (Dax Shepard) and needs a place to live. Hey, we have to get Felix and Oscar in the same apartment somehow.

While first-time writer-director (and former “SNL” scribe) Michael McCullers succeeds at that maneuver, he fails to come up with much in the way of convincing comic friction. From this point forward, the movie unspools like a laundry list of sight gags and random character quirks. We’re supposed to believe, for example, that Kate would baby-proof her place eight months before the bundle of joy is even due. This enables hilarity to ensue when Angie can’t figure out how to unlock the toilet and is caught peeing in the bathroom sink instead. You’ve seen the trailer. The houseguest also sticks wads of gum on the underside of a coffee table. These are the picture’s high points.

It takes the low road to laughs surprisingly often, too. McCullers mercilessly milks a lisping birth coach for cheap titters. There’s a running gag having to do with the fact that Weaver’s character not only gets pregnant but produces twins. Get it? She’s going on 60. Steve Martin is enlisted to play Fey’s boss, a ponytailed blowhard who thinks he’s some kind of new age guru. At one point, he offers to whisper the secret of success in Poehler’s ear. Spoiler alert: It’s a penis joke.

The filmmaker attempts to enliven things with a couple of late-inning surprise twists. But not only are they too little, too late to save this prenatal piffle, they’re likely to take very few in the audience by surprise. For one thing, said plot turns are stunningly predictable. For another, we’re talking about viewers who are perhaps a watt or two brighter than the average moviegoer. The film’s target demo is Tina Fey’s fans, after all, not Chuck Norris’.

From “SNL” to Mean Girls to “30 Rock,” the work Fey writes and appears in has been consistently of the highest comic quality. The downside is that now she’s earned the option of broadening her career — experimenting with the possibility of being a movie star, an actress hired by other people to perform material written by other people. If Baby Mama is any indication, Fey’s core audience could be in for a disorienting experience. She’s set the bar high to get where she’s gotten, and reaching the next level may necessitate lowering it. In this slapdash riff on motherhood, she comes close to tripping over that proverbial bar — no doubt something very few of her fans were expecting.