The thirteenth and final season of King of the Hill originally aired Sunday nights on FOX from September 28, 2008 to September 13, 2009. Four of the thirteen episodes produced for this season originally aired in syndication between May 3, 2010 and May 6, 2010.
Bill's love of sugary snacks causes diabetes. After a doctor tells Bill that he will lose his legs he decides to start using a wheelchair. Once he is wheelchair bound he finds camaraderie with Thunder, a wheelchair sports enthusiast. Things turn around for Bill until Thunder finds out that Bill does not really need the wheelchair.
Hank helps Strickland Propane go green after a local paper slams the company for dumping old propane tanks into the river. Meanwhile, Dale seizes the opportunity to impress the ladies by organizing an earth benefit concert.
Hank and the guys do a good deed when they fix-up a neighborhood house, however after Ted Wassonasong buys the house he decides to knock down the house and build a mansion.
Hank has bad feelings when Mr. Strickland decides to create a MySpace page for Strickland Propane. Hank's fears come true when Donna posts personal videos and information to the web site.
In order to raise the school's average for standardized tests, Principal Moss classifies Bobby as a low achievement student. However, the plan backfires after Bobby is placed in a class where he no longer has to do homework and doesn't have to take the tests.
Peggy, Minh and Dale play the stock market together, however they lose money in their initial investment. To improve their odds they decide to study the consumer habits of an "average man" and Bill becomes the subject of their study. Meanwhile, after Peggy buys the family a new flat screen TV, Hank and Bobby have difficulty figuring out all the advanced features.
Hank tries to help Bobby become a member of the Order of the Straight Arrow, but he disagrees with the "Arrowmaster" who is a new member of Arlen. Meanwhile, Peggy gets involved in the disagreement as she is the local Welcome Wagon representative.
Lucky's sister Myrna and her children attend a baby shower in which Peggy is throwing for Luanne. It doesn't take long before Myrna and Peggy clash over how the children will be raised by Luanne, with Peggy wanting the good, old fashioned skills where as Myrna likes the more modern way and by the book.
The Propane Hall of Fame is inducting Buck Strickland this year and he has asked Hank to come with him to make sure he stays out of trouble. This becomes a hard task after Buck meets his illegitimate son while at the event in Memphis.
Bobby is left waiting at the mall when Hank and Peggy's date goes long. Feeling his parents' guilt, Bobby uses the incident to pit each against one another to show him their affection. Soon, Peggy and Hank stop giving him anything Bobby wants and he demands they spend more time with him.
Hank and the gang get a rematch for the high-school championship game they lost, when Bill accidentally breaks Hank's nose during a practice. He gets it fixed by a plastic surgeon and loves his new nose---maybe too much.
After Peggy finds out that she is not cool she befriends one of Arlen's most glamorous and cool moms in an effort to learn how to be cool. Bobby befriends her daughter, a girl named Michael Savage.
After Nancy takes a glamorous new job in Dallas and temporarily leaving Dale behind he finds the freedom of the bachelor life too hard to handle.
Bobby is offered an intervention at the church, after Hank becomes upset by his misbehavior. Meanwhile, Hank and his pals challenge a rival neighborhood to a Fourth of July fireworks showdown
Hank discovers that his father's last requests are a collection of bizarre tasks including the wish to have his ashes flushed down a toilet that General George S. Patton once used. Meanwhile, Bill and Dale bicker over an empty beer can.
Hank is troubled when Bobby's Little League Coach is hassling Bobby about his lack of ability until Hank realizes that the Coach is only trying to make Bobby a better player.
Luanne tries to become a breakout star in the children's entertainment industry.
After Boomhauer trades houses with a Canadian family for the summer the Arlen gang tries to make some new neighbors at feel welcome. However it soon becomes apparent that Canadians and Arlenites do not see eye to eye.
Bobby becomes quite the ladies' man when several girls in his class consider him a potential date for the Homecoming dance, but Hank is worried that Bobby is being used.
In the series finale, Bobby's new found passion for judging the quality of meat brings the Hill men closer as they bond as father and son for the first time. Jeff Boomhaeur's job as a Texas Ranger is finally revealed.