“You’re prettier than I am,” mumbles scruffy slacker Ben (Seth Rogen) to nymph Alison (Katherine Heigl) as they tumble into bed. That genetic inequity lasts into the following morning, when Alison gives Ben the brushoff he’s been expecting all along. Four weeks later, thanks to a misunderstanding about Ben’s rubber, Alison is pregnant, and this mismatched couple now has to decide if they have anything in common besides the baby they’re making. Can a hot, ambitious E! Entertainment reporter find happiness with a guy who lives for his bong and wears the same brown T-shirt day after day? Knocked Up draws from the same well of scattershot comic sociology that irrigated writer-director Judd Apatow’s most recent smash, The 40-Year-Old Virgin. (Why do all his titles sound like working titles?) The plot, as such, is a flatbed truck filled with bales and bales of talk, most of it quite funny, some of it uncanny. The men in Apatow’s world can riff on anything—Steely Dan, Cirque du Soleil, the number of chairs in a hotel room—and the suspicion always lurks that they need to talk, that chatter is how they mask the terror they feel around women. Not to mention their feelings for one another. (If there’s a love match to be found anywhere, it’s between Rogen and Paul Rudd, who pick up pretty much where they left off with their “You know how I know you’re gay?” jousting from Virgin.) What saves Apatow from being a multiplex Mamet is his sincere, if sporadic, interest in the female animal. Even Alison’s harridan sister (Leslie Mann) has moments of hard-earned pathos, and come to think of it, pretty much every speaking part in Knocked Up, from bar bouncer to gynecological assistant, gets a spot in the sun. Which may explain why the movie takes an unconscionable two-plus hours to reach its foregone conclusion. That’s just enough running time to expose the limits of Apatow’s fundamentally static dramaturgy—and the limits of Rogen, an amiable supporting cat who lacks the chops to build and differentiate his scenes. In this regard, too, he’s outclassed by Heigl, whose feral labor sequence is such a wonder of emotional commitment that she seems to belong to another world—where people don’t just talk but listen.