Victor Aaron, the original voice of John Redcorn, died in a road accident after recording his lines for his only episode "The Order of the Straight Arrow." Rather than drop the character, they got a replacement: Johnathon Joss.
Brittany Murphy (the voice of Luann Platter and the voice of Joseph Gribble before he hit puberty) was a cast member on the show and did die, but her death came three months after FOX aired the last episode ("To Sirloin With Love," not "Just Another Manic Kahn-Day"). Still, for any fan who wants King Of the Hill to come back, it probably won't happen without Brittany Murphy.
Bill and Buck Strickland are played by Stephen Root, who also played Chode (the horny, cheapskate protagonist on Tripping the Rift). Chode is more like Buck Strickland than he is Bill.
Once again (cf. Codename: Kids Next Door and Futurama), Lauren Tom plays an Asian girl and her mom ("Connie" [Kahn, Jr.] and Minh). The only difference with this one is that Connie isn't an Asian Airhead (in fact, she's the archetypical Asian kid character who is forced by her parents to be more intellectual and cultured than her American counterparts).
Peggy Hill was also the voice of Coach Doogan on Pepper Ann (Kathy Najimy), meaning that Najimy went from voicing a full-time middle school gym teacher to a substitute middle school Spanish teacher (who later wrote for the town newspaper and went into real estate).
Some of the celebrity voices they have you wouldn't know unless you watched the episode a second (third, or fourth) time (cases in point: Owen Wilson as a sexually insecure man who almost marries Luanne on "Luanne Virgin 2.0," Johnny Depp as a yoga instructor on "Hank's Back," and Reese Witherspoon as Debbie Grund on the two-part episode where she's found shot to death in a Dumpster, but it turns out she accidentally killed herself because she was stupid enough not to put the safety on her gun and to take it with her while she got nachos at the Get In-Get Out), while others (like Snoop Dogg as Alabaster Jones on "Ho Yeah!", Alan Rickman as King Phillip on "Joust Like a Woman," or Chris Rock as Booda Sack on "Traffic Jam"note not the later episodes where Phil LaMarr replaced Chris Rock) are fairly obvious.
Missing Episode: Because FOX wanted to get rid of the show as quickly as possible (as they needed room for Bob's Burgers and The Cleveland Show), the network decided to pick two episodes out of the last six they ordered to air and scrap the remaining four. The last two episodes that aired were: "The Boy Can't Help It" (where Bobby is taken advantage of by three high school girls) and "To Sirloin With Love" (where Hank discovers Bobby's talent for identifying flaws in beef cuts and puts him on Heimlich County's community college meat inspection team). The four episodes that didn't air on FOX aired in network syndication, on [adult swim], and are on Netflix. Those episodes are: "The Honeymooners" (Hank's mom breaks up with her longtime boyfriend and dates a man she barely knows), "Bill Gathers Moss" (Bill rents his house out to roommates on Craigslist), "When Joseph Met Lori and Made Out With Her in the Janitor's Closet (Exactly What It Says on the Tin), and "Just Another Manic Kahn-Day" (Hank recruits Kahn to build a grill by forcing him not to take his medication, which he needs for his bipolar disorder while Bobby tries to find the humor in an old comedy record Peggy likes).
The Other Darrin: In John Redcorn's first speaking appearance (on the season one episode "Order of the Straight Arrow"), he was played by Victor Aaron. When Aaron died in a car accident, Johnathan Joss was hired as the new Redcorn for the rest of the series.
M.F. Thatherton was played by Burt Reynolds in his first appearance. In all other appearances, he was played by Toby Huss (whom many Pete & Pete fans will recognize as the guy who played Artie, The Strongest Man in the World).
Hank's mom, Tilly Hill, was played by three actresses: First by Tammy Wynette for two episodes in season 2. When Tammy died, she was replaced by Beth Grant during season 3 (plus one previously unaired episode). Finally, K. Callan voiced Tilly in two season 5 episodes and one season 8 episode.
Roger 'Booda' Sack was played by Chris Rock in his first appearance, and was played by Phil LaMarr (doing a Chris Rock impression, the same one he did on a couple of episodes of MADtv) in subsequent appearances.
Special circumstances note Brittany Murphy's career, which was expanding at the time of season 4 are behind this one, but it's worth noting that for the first four seasons (and a few episodes in season 5) Joseph Gribble was played by Brittany Murphy. When Joseph hit puberty on the episode "I Don't Want To Wait For Our Lives To Be Over," he was voiced by Breckin Meyer.
Screwed by the Network: An odd case. KOTH was a huge hit in its first few seasons, but Fox damaged the show's ratings by constantly shuffling its time slot. Even during its last few seasons, when it returned to the original 8:30 Sunday slot, it was pointedly treated as the lesser partner in Fox's "Animation Domination" block, receiving negligible promotion compared to The Simpsons or Family Guy.
Tuckerization: Bill Dauterive is named after script writer Jim Dauterive.