Unwanted pregnancy might sound like a risky subject for slapstick comedy, but Knocked Up is from writer-director Judd Apatow--so we are in the hands of a man who likes to push things. And like Apatow's predecessor, The 40-Year-Old Virgin, Knocked Up is a shaggy crowd-pleaser, a comedy strewn with vulgarity but with a sweet heart at its center. A one-night stand between the utterly mismatched Ben (Seth Rogen, his first starring role) and Alison (Katherine Heigl) results in said pregnancy, and the two people reunite for mutual support--even though they barely know each other. Ben's a slob who lives...