Two people who have a one-nighter realize they aren't right for each other, and then a few months later they learn they are going to have a baby. Mismatched pair create lots of laughs Some of the most successful comedies of recent years have struck a balance between raunchy gags for men and relationship humor for women. One of the best of this two-headed species was 2005's "The 40 Year Old Virgin.

" Judd Apatow, the co-writer and director of that film, returns to that same territory in "Knocked Up." Although this story about a mismatched couple expecting a baby strains credibility and sometimes pushes the limits of good taste, it delivers plenty of belly laughs. Seth Rogen, who played a sidekick in "Virgin," stars as Ben, an affable slacker who shares a Los Angeles crash pad with several pals.

They fantasize about starting a celebrity-nudes website; but mostly they just get stoned and fling good-natured insults at each other. It's a rather narrow and unflattering representation of contemporary manhood, but it's necessary to set up a comedic dichotomy with the ambitious Alison (Katherine Heigl), whom Ben meets at a nightclub. Alison and her older sister Debbie (Leslie Mann, the scene-stealer from "Virgin" who is Mrs.

Judd Apatow) are celebrating Alison's promotion to an on-camera job at an entertainment-news channel. After a few-too-many drinks, Alison takes Ben back to her place for a nightcap. Eight weeks later, Alison discovers she is pregnant and has to break the news to the doofus she thought she would never see again.

She announces she is going to keep the baby and, even less plausibly, invites this doughy loafer to stake a place in her world. Without much of a courtship, Alison and Ben are soon holding hands and shopping for baby clothes. Debbie is rightly skeptical of this adolescent oaf, but Ben develops a crude camaraderie with her unhappy husband, Pete (Paul Rudd).

Apatow's script is often fiercely funny, but sometimes it teeters uneasily between shock value and sentiment. The problem may be that Rogen (in his first starring role) and Heigl (who has the elusive charm of Lisa Kudrow or Diane Keaton) are such likable performers that we root for a happy ending that doesn't make rational sense. But even with its conflicted values, "Knocked Up" is a reminder that a bundle of joy can come from strange bedfellows.

Two people who have a one-nighter realize they aren't right for each other, and then a few months later they learn they are going to have a baby. 55. 2543- Two people who have a one-nighter realize they aren't right for each other, and then a few months later they learn they are going to have a baby.

Mismatched pair create lots of laughs Some of the most successful comedies of recent years have struck a balance between raunchy gags for men and relationship humor for women. One of the best of this two-headed species was 2005's "The 40 Year Old Virgin." Judd Apatow, the co-writer and director of that film, returns to that same territory in "Knocked Up.

" Although this story about a mismatched couple expecting a baby strains credibility and sometimes pushes the limits of good taste, it delivers plenty of belly laughs. Seth Rogen, who played a sidekick in "Virgin," stars as Ben, an affable slacker who shares a Los Angeles crash pad with several pals. They fantasize about starting a celebrity-nudes website; but mostly they just get stoned and fling good-natured insults at each other.

It's a rather narrow and unflattering representation of contemporary manhood, but it's necessary to set up a comedic dichotomy with the ambitious Alison (Katherine Heigl), whom Ben meets at a nightclub. Alison and her older sister Debbie (Leslie Mann, the scene-stealer from "Virgin" who is Mrs. Judd Apatow) are celebrating Alison's promotion to an on-camera job at an entertainment-news channel.

After a few-too-many drinks, Alison takes Ben back to her place for a nightcap. Eight weeks later, Alison discovers she is pregnant and has to break the news to the doofus she thought she would never see again. She announces she is going to keep the baby and, even less plausibly, invites this doughy loafer to stake a place in her world.

Without much of a courtship, Alison and Ben are soon holding hands and shopping for baby clothes. Debbie is rightly skeptical of this adolescent oaf, but Ben develops a crude camaraderie with her unhappy husband, Pete (Paul Rudd). Apatow's script is often fiercely funny, but sometimes it teeters uneasily between shock value and sentiment.

The problem may be that Rogen (in his first starring role) and Heigl (who has the elusive charm of Lisa Kudrow or Diane Keaton) are such likable performers that we root for a happy ending that doesn't make rational sense. But even with its conflicted values, "Knocked Up" is a reminder that a bundle of joy can come from strange bedfellows. Two people who have a one-nighter realize they aren't right for each other, and then a few months later they learn they are going to have a baby.