Two scenes stand out in "The Back-up Plan," Jennifer Lopez's long-overdue return to comedy after years of morose movie dramas, music videos and careful cultivation of her celebrityhood.

There's a birth scene, a screaming, heaving, New Agey single-mothers group gathering as one of their number graphically brings a newborn into a world of drums, chants and comic chaos.

And then there's Robert Klein, playing an ob-gyn trying to get the boyfriend-but-not-the-baby-daddy (Alex O'Loughlin) to grow up as he performs a pelvic exam on the artificially inseminated expectant mom (Lopez).

"Vagina," Klein snaps. "Vagina vagina vagina vagina!"

All around the periphery of this variation on a "Baby Mama" theme are funny best friends (Michaela Watkins, Anthony Anderson), cute dogs and zingers about the shock impending parenthood has on the woman who has planned it, and the boyfriend she was a little slow telling about it after they met.

There isn't much chemistry between the leads. Lopez plays Zoe, a thirtysomething pet store owner who has decided to go it alone when it comes to having a baby. O'Loughlin ("Whiteout," "Three Rivers") co-stars as Stan, the pushy-charming cheese merchant she keeps bumping into.

"I'll give you a taste of my cheese ... Let me rephrase that."

Director Alan Poul, a TV vet ("Big Love," "Swingtown"), commendably makes the most of what he has to work with. That would be Lopez — who is gorgeous, a little over-dressed for a Manhattan pet-store owner and properly comically nonplussed — and some of her supporting players plus the film's occasional can't-miss funny scene.

But for all the profanity (quite a bit) and sexual sass, this CBS Films product plays even more like a TV movie than its debut project, "Extraordinary Measures." There's Linda Lavin (TV's "Alice") playing Zoe's granny and a feeble-looking Tom Bosley ("Happy Days") as granny's suitor. And TV writer Kate Angelo's tired "Becker"/"Bernie Mac Show" jokes and rhythms don't help.

These problems aren't obvious when Lopez is interacting with critters or character actors. But O'Loughlin is the very definition of comic dead weight.

Imagine making Greg Kinnear carry half of "Baby Mama," or sending Tina Fey out with Matthew Fox on "Date Night," and you'll get the picture.

O'Loughlin has landed the lead in the "Hawaii Five-0" TV remake, so good for him. Then again, nobody fondly recalls the comic stylings of Jack Lord, do they?