Cast member Katherine Heigl poses at the premiere of 'Knocked Up' in Los Angeles, California, May 21. - REUTERS

(AP):

Everything you've heard about Knocked Up is true: It's even more riotously and consistently hilarious than its predecessor, Judd Apatow's 2005 sleeper hit The 40-Year-Old Virgin, with even greater heart.

As writer and director, Apatow has the rare ability to find just the right tone all the time, a bold yet delicate balance of humor that's raunchy without being mean, sweet without being saccharine.

Knocked Up also features a cavalcade of pop culture references that never feel gratuitous, as well as some in-jokes that never seem smug.

Here's how good Apatow is: He even manages to make Ryan Seacrest funny, in one spectacular scene in which the 'American Idol' host takes a sledgehammer to his self-important image.

Scene-stealing performance

Seth Rogen, who we already knew was funny from his scene-stealing performance in Virgin, emerges as an unlikely but likeable leading man as Ben Stone, a goof-ball of a slacker-stoner who enjoys a drunken romp with Alison Scott (Katherine Heigl from "Grey's Anatomy" showing an unexpected knack for comedy), an up-and-coming entertainment reporter who's way out of his league.

Eight weeks later, she realises she's pregnant and, to borrow from Madonna, she's made up her mind, she's keeping her baby, forcing both of them to make major changes in their lives.

Clearly these people are totally wrong for each other. Ben is round and hairy; Alison is leggy and blonde. He sits around all day with his equally unmotivated buddies, working on a website that lists the exact moment when actresses get naked in movies; she wakes up early, spends time with her family and takes her job seriously at E! Entertainment Television.

But they must get to know each other, first as friends and then possibly as something deeper, if they're going to make this work. It doesn't exactly help that their primary example is Alison's older sister Debbie (Apatow's radiant wife, Leslie Mann) and her husband, Pete (Paul Rudd, always a subtle comic talent), who don't have much in common anymore besides their two kids.

On Ben's side, there's even less help. The friends with whom he shares a tract house in the San Fernando Valley (Jason Segel, Jonah Hill, Martin Starr and Jay Baruchel, all old pals from Virgin and Apatow's short-lived TV shows Freaks and Geeks and Undeclared) say they support him but they'd have no idea what to do with a baby, and they're too high all the time to figure it out.

"Knocked Up" starts out with a one-night stand, but in the end it turns out to be a movie about loyalty. And except for being a bit on the long side, which you won't mind because you'll be having too much fun; it is pretty close to perfect.