Fox's King of the Hill just ended its 10th season, and 200th show, with a gimmick episode. It featured Lucky, a new character voiced by rocker Tom Petty, proposing to Hank Hill's niece Luanne. Other characters on the series are getting new jobs or just vanishing altogether. You could say that it's a case of a long-running show trying to shake things up and make changes -- except that for King of the Hill, the problem may be that those changes are mostly cosmetic.

John Altschuler, who has executive-produced King of the Hill for the last five seasons, admits that the introduction of new characters is a way to keep the show fresh: "It really isn't a matter of trying to shake things up as trying to avoid doing the same show again." But to some extent, King of the Hill has been doing the same shows again this past season. Every season features several episodes based on a familiar formula: Hank's son Bobby gets a new hobby that distresses his father, and Bobby learns in the end that his father was right. This season we saw Bobby becoming a clown, a panhandler, and an assistant to a professional pooper-scooper. These episodes were funny, but similar to episodes the show has done before, where Bobby got involved with things like male modelling or the(originally Canadian, it was pointed out)pastime of dog-dancing. Add in the dozens of episodes about the stolid Hank's conflicts with New Age liberals, and we have a show whose characters haven't changed much since the first season.

Any long-running sitcom has the problem of trying to justify its presence on the air: what is there left to say about characters whose quirks have been explored over and over, especially since the show would be finished if they changed too much? With King of the Hill, Altschuler and his producing partner Dave Krinsky have tried to nibble around the edges a little by keeping the characters exactly the same but changing their surroundings a little. "What we realized," Altschuler says, "is that it is important to keep the characters constant, but that can become redundant unless you can put them in different situations."

And so with Hank's wife Peggy, the producers dropped her regular job(teacher)and gave her a rotating series of jobs: a journalist this season, a realtor next season. Altschuler explains: "We like using her to explore different situations through new attempts at finding the right job for her. This is a situation that many moms we know find themselves in when the kids grow up." But the characterization of Peggy remains the same -- a know-it-all who gets into trouble by overestimating her own intelligence -- and that can make her storylines somewhat repetitive: as with Homer Simpson, we've seen her get into this kind of trouble before in the old job.

The other way to keep a sitcom going is to add new characters in selected episodes. "If we didn't start integrating new characters," Altschuler says, "the show would be over." But the newest character, Lucky, comes off to some fans as the kind of snaggle-toothed, stereotypical redneck the show was originally set up to avoid(Greg Daniels, the co-creator, prided himself on "not doing Hee Haw"). A lot of King of the Hill fans have reacted to the addition of Lucky much the way Flintstones fans reacted to the little green alien the Great Gazoo.

The season finale was a reminder of what can go wrong with a new supporting character like Lucky: when he appears on the show, he seems to suck some of the life out of established supporting characters. Luanne, originally one of the four most important characters on the show(a representative of "trailer-trash" culture with a funny-sad backstory), now plays second fiddle to Lucky on the rare occasions when she appears. Other characters have disappeared from the show altogether: Cotton Hill, Hank's hilariously misanthropic war-hero father, hasn't appeared in over a year. You could argue that King of the Hill has fallen into the trap of introducing new gimmicks and characters instead of developing the old, familiar characters.

On the other hand, that may be enough: King of the Hill is still funny and still popular enough to get another season after this one. And as Altschuler points out, most people at Fox seem to think they're doing fine: "One of the reasons the show is back for another year is that people have felt that the show is on track, yet still able to feel fresh." And if the price of freshness is a rock star guest-voicing in a gimmicky marriage-proposal episode, well, mos

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