Writer-director Judd Apatow's big-screen follow-up to 2005's "The 40-Year-Old Virgin," "Knocked Up" is every bit its equal but not exactly a signifier of growth for the filmmaker. Serving as companion pieces as well as stand-alone efforts, both pictures are comical studies in a grown man's arrested development and his ultimate coming-of-age. Whereas "The 40-Year-Old Virgin" was about the title character's steps toward sexual discovery and navigating male-female relationships, "Knocked Up" sheds a sometimes painfully honest light on what might happen if a happy-go-lucky 23-year-old slacker was suddenly faced with the prospects of becoming a father. A bawdy romantic comedy as well as a warmly observed slice-of-life, the film is knowledgeable in the ways it chooses to tell its story without compromising the audience's intelligence. At the same time, it treads upon familiar territory and is so predictable that there is no reason for the extensive 132-minute running time.

Jobless and coasting on the dwindling insurance money he received from being hit by a car years ago, Ben Stone (Seth Rogen) spends his days getting stoned with his friends and plotting out a web venture about female nudity in film. Alison Scott (Katherine Heigl) is a young working gal living with older sister Debbie (Leslie Mann), brother-in-law Pete (Paul Rudd), and their two children. When Alison receives a promotion at the E! network as an on-air reporter, she hits the club scene to celebrate and ends up sharing a drunken one-night stand with Ben. The two of them have little in common, a fact that becomes clear to Alison the next morning over breakfast, and their relationship would appear to end as soon as it begins. Eight weeks later, however, she finds out she is pregnant, putting a corkscrew into her ten-year plan and forcing her to come clean to Ben. With a child on the way, these two polar opposites decide to give it a go together.

"Knocked Up" is quite similar to "The 40-Year-Old Virgin," if not in the particulars of the story than in the overall progression of the narrative. It is blindingly obvious how things are going to turn out in the end, but both movies are R-rated crowd-pleasers for adult audiences that have undeniably big hearts. They also have many of the same pitfalls. "Knocked Up" contains some heavy material and a bunch of worthwhile life lessons, but it is told with a light and silly touch that clashes with too many supporting characters and a boundless editing job that would greatly benefit from more judicious cutting.

On its own, a monologue from an overstressed bouncer who is tired of having to pick and choose who gets special treatment at the door is eye-opening and very funny, but within the confines of this film, it is unnecessary and could have shed five minutes off the length had it ended up on the cutting room floor. The same goes for some of the scenes where Ben hangs out with his daffy pothead best friends/roomates (Jonah Hill, Jay Baruchel, Jason Segel, Martin Starr). These side characters' antics are amusing and their dialogue contains a number of tart zingers, but none of them have personal arcs nor a whole lot of stake in the main storyline. Before long, they get to be too much of a good thing and slow down the pacing.

When the attention is on Ben and Alison's burgeoning love and affection for each other, as well as the various hang-ups, conflicts, insecurities and roadblocks that arise in the meantime, "Knocked Up" shines with the glow of a pregnant woman in her second trimester. Their romance seems like a long shot at first—he is chubby and misdirected, she is gorgeous and knows what she wants—but before long the relationship adopts a true sweetness and believability that gives the viewer something to cling to and really care about. Ben might still be a little immature and not sure if he is ready to leave his days of partying and freedom behind him, but he is a nice and caring guy who valiantly steps up to the plate and tries to be there for Alison.

In his first aim at being a leading man, Seth Rogen (2006's "You, Me and Dupree") is a winning screen presence whose oafish side and everyman looks makes him all the more relatable to audiences. Rogen is so natural that he barely appears to be trying, and that is the key to success for an up-and-coming actor who could very well go the distance in having a long-term screen career. As Alison, Katherine Heigl (2005's "The Ringer") gets to show a looser side and more of a comedic edge than she is able to on TV's "Grey's Anatomy." Heigl, like Rogen, is innately likable, and she has the dramatic experience to effortlessly pull off the emotions of a woman thrown a curveball in her life and struggling to make the best of it.

In the two other major roles, Leslie Mann (2002's "Stealing Harvard") and Paul Rudd (2007's "Reno 911!: Miami") are at their best as struggling married couple Debbie and Pete. Mann avoids the risk of seeming shrewish and overbearing as her character, a woman in her thirties who is afraid of leaving her youth behind and questioning the strength of her marriage, is fleshed out enough to understand where she's coming from. As for Rudd, he has perfected the part of the friend to the central character and is ready to get a high-concept comedy of his own. When Pete and Ben hit the road for Vegas and experience a one-of-a-kind mushroom trip that includes attending a Cirque du Soleil show and counting the number of different chairs in their hotel room, it is uproarious to behold.

"Knocked Up" is a motion picture not about settling, which it could have bleakly become, but about growing up and finding one's soul mate in the least likely of situations. Raunchy in spurts but more often relying on witty banter and empathetic situations to carry the laughs home, "Knocked Up" is wiser than the genre typically allows and grounded in reality rather than a sitcom world. With that said, writer-director Judd Apatow's next goal should be to tighten the reigns of his overstuffed screenplays, learn when to part with the extraneous material, and visually open his movies up beyond their current point-and-shoot style. "Knocked Up" is a good film. Lurking beneath the surface is a great one just dying to break free.