I thought Knocked Up had a real strong current of pathos undermining the whole thing. It was funny in spots but the premise turned out to be sad what with the obvious mismatch between the girl and the stoner, the stoner's inability to get a grip (at least initially), and the forced relationship. In addition, Katherine Heigl never took off her bra and man, is Harold Ramis getting old!
Maybe my head was just in the wrong place for the movie.