Successful sitcoms don't exactly change from season to season--why mess with a winning formula?--but they do evolve. So it is with the fourth season ofRules of Engagement, offered here with all 13 episodes on two discs (there are no bonus features). Developments this time around include a larger role for Timmy (Adhir Kalyan), the forever-suffering assistant to the insufferable Russell Dunbar (David Spade); the efforts of Jeff and Audrey Bingham (Patrick Warburton and Megyn Price) to get pregnant, involving fertility drugs and a surrogate; and, after a very long engagement, the announcement of a wedding date for young couple Adam Rhodes (Oliver Hudson) and Jennifer Morgan (Bianca Kajlich). The former is especially welcome; bits like the scene in "Flirting" in which Russell dispatches Timmy to find the cell phone he left at the home of his latest one-night stand (who turns out to be a member of a bible study group) are always good for a laugh. But the show's main attraction remains the relationship between Jeff and Audrey, now in their 15th year of marriage and still sorting through various issues (keeping their sex life fresh, Jeff's realization that he once dated a contestant on a reality dance show, and communication in general) in a manner that's both amusing and realistic enough to be convincing. Warburton's deadpan, wisecracking Jeff may be a bit of a Neanderthal--things like texting, video games, and couples therapy ("Why deal with stuff when you can just push it down inside and go on with your life?") remain well beyond his grasp--but he's not a villain, and in the end he almost always does the right thing. Spade's Russell is another story. It's hard to love a glib, smarmy manipulator who shamelessly uses women and treats his assistant like dirt, but he's not irredeemable. Indeed, Russell shows some unexpected humanity and vulnerability in a two-episode story arc involving the beautiful young woman whom Timmy's family has determined he is to marry; Russell also gets some comeuppance in "Free Free Time," when he and Timmy attend a party celebrating the launch of a new video game designed by a former assistant… and featuring Russell as the game's hapless gnome victim.--Sam Graham