For the most part, serialized storytelling has melded well with the episodic tradition of TV. The episodic structure of the medium means that unlike a novel or film, a TV series' plot can be tweaked at any time for the better (see Breaking Bad's Jesse Pinkman, who was originally slated to die in season one, or Justified antihero Boyd Crowder, who wasn't even intended to survive the series' pilot). And there's plenty to be said for rewarding regular viewers with callbacks and references, which is only possible when there's continuity from episode to episode. The best contemporary sitcoms, like Parks and Recreation or Community, have earned additional critical acclaim and viewer loyalty by increasing their number of recurring plot arcs and inside jokes. But dramas have been the primary beneficiaries of the serialization trend.
But there's one key element of TV drama that remains an awkward fit when a serial narrative is grafted onto an open-ended, episodic structure: the central protagonist. What we're beginning to see is a TV landscape of dynamic, evolving characters who surround a protagonist of frustrating rigidity. Though nearly any modern TV drama could fit this analysis, let's start with Mad Men, which returns to AMC for its fifth season one month from today. Betty Francis (formerly Betty Draper) has had a stunningly propulsive character arc—morphing, in four seasons, from meekly deferential housewife to strong-willed self-defender. Peggy Olsen has risen up the ranks of the advertising world, and consequently become more confident in her personal and professional talents; Pete Campbell, who sniveled his way through the first season, has become a capable businessman and husband.
And then there's Don Draper, who spent the first season drinking and carrying on with young, artsy brunettes ... and ended the fourth season drinking and carrying on with a young, artsy brunette. This is not necessarily a fault with Mad Men; there's nothing inherently wrong or unrealistic about a static main character (most tragedies are, after all, built around them). But I have a small, nagging feeling that Mad Men won't let Don Draper evolve. Series-best fourth-season episode "The Suitcase" made Don Draper's rock-bottom so visceral, and his subsequent guilt and recovery so honest, that it wasn't just disappointing to watch him make the same mistakes in the season's finale—it was implausible. But when your show is a hit—and your lead character, for all his drinking and womanizing, is a pop culture icon—fundamental change may be a risk too big to take.
This problem is even more pronounced in series like 24 or The Walking Dead, in which the main character routinely faces death. By the end of its eight seasons, 24's Jack Bauer had bested so many villains that the series' sense of danger was all but gone (one fan video measures Bauer's on-screen kill count at 265 over eight days). The Walking Dead hasn't been on for nearly as long, but protagonist Rick Grimes has already escaped dozens of zombies (and the occasional villainous human). Belief can only be suspended so far, and though the two hours of an action film are generally plausible enough, the dozens of hours that makes up TV's action dramas stretch suspense to the breaking point. No series (with one recent, very dramatic exception) is likely to kill off its main character, since that person tends to be its most recognizable, most liked, and the focus of its primary narrative and marketing campaign.