Continuity mistake: Peggy Hill's mother seems to change over the course of the show. Prior to the ninth season, whenever Peggy's mother is seen (in the present or in flashbacks), she is portrayed as an older version of Peggy. In the ninth season's premiere episode, Peggy's mother is a lean, leather-skinned rancher who disdains Peggy and lives on a secluded ranch. The change in facial features and appearance is too much to just be a change in style as well.
Continuity mistake: (Episode 9-13: Gone With the Windstorm) Just after Dale, Nancy and Peggy get past the police blockade in the news van there is an overhead shot of the van and you can see Dale doesn't have his fake moustache on anymore. The next shot he is taking off the fake moustache.
Continuity mistake: (Season 11, Episode 5 - Hank Gets Dusted) While Hank is reminiscing about the car with his father he is in the garage and does not realise he is being filmed by the cameras. The following scene, the filming crew is watching the footage in the truck and the shot shows the camera angle is now different and would only be possible if Hank was standing in the alley outside his house.
Continuity mistake: Episode 9-13, 'Gone With the Windstorm': As Hank jumps out of the closest to scare the boy that is scaring Bobby, we see the contents of the cupboard as well. We see a shelf with a large number of boxes. Clothes rail with many clothes hanging on it. Finally an assortment of objects on the ground. When Hank leaves and the father is wondering where his son has disappeared to we see inside the cupboard again. Everything including the shelf, clothes and clothes rail have disappeared. The only thing remaining is one small box in the left corner.
Continuity mistake: Throughout the first couple of seasons, Hank's first truck switches between automatic and manual transmissions. This is most obvious in the episodes "Chasing Bobby", in which it has a manual transmission and "Texas City Twister", in which it has an automatic transmission.
Other mistake: In the season four episode "Nancy Boys", when Nancy calls John Redcorn and tells him that she wants him back, he says, "I'm thirty-six years old. I don't need this crap." Later, in the season nine episode "Redcorn Gambles With His Future", while John is talking to Hank, he mentions waking up one day and realizing that he is forty. If four years had passed since his break-up with Nancy, then Bobby and Joseph would now be sixteen and at least sophomores in high school, but they are still in middle school.
Continuity mistake: The ages of Hank, Peggy, and Didi (Hank's stepmother) are inconsistent throughout the show. In the season one episode "Shins of the Father", Hank states that Didi went to kindergarten with him, so they are the same age. In the season four episode "Peggy Hill: The Decline and Fall", Hank mentions that Didi is three years older than Peggy. Therefore Hank is also three years older than Peggy, if he and Didi were in the same kindergarten class. Finally, in the season five episode "Luanne Virgin 2.0", Hank says that he and Peggy were already married when they were eighteen. This is not possible if he and Didi are the same age and went to kindergarten together. He would have had to marry a fifteen-year-old Peggy if he was married by age eighteen.