Judd Apatow made his bones as a comedy writer for Ben Stiller and Garry Shandling, but his own projects--the TV series Freaks and Geeks and Undeclared and the sleeper theatrical hit The 40-Year-Old Virgin--have a sensibility all their own, loyal to the tradition of raunchy adolescent humor but also sneakily astute in their emotional truths. Like Virgin, this story of a lazy slob (Seth Rogen) who drunkenly impregnates a beautiful TV host (Katherine Heigl of Grey's Anatomy) shows how young men and women tend to view each other as the gateway to adulthood, though in this case the looming responsibility of childbirth makes the passage even more terrifying. Funny, honest, and generous, this is mainstream American comedy at its best. Apatow directed; with Paul Rudd, Leslie Mann, Martin Starr, Jason Segal, and Jay Baruchel. R, 129 min. Reviewed this week in Section 1. a Century 12 and CineArts 6, Cicero ShowPlace 14, City North 14, Crown Village 18, Ford City, Gardens 7-13, Lake, Lincoln Village, Norridge, River East 21, 600 N. Michigan.