Continuity mistake: When Bo is being chased by Campus Police, he tells everyone to "Get Skinny" as he squeezes through two cars, and leaves quite a little bit of damage on each side. Yet when Bo is driving on the rally track, there's a shot from the right and no damage is visible.
Continuity mistake: When Luke and Uncle Jesse are in Boss Hoggs' car, in the racing scene towards the end of the movie, Jesse is just about to start lighting and throwing the jars of moonshine. Just before he does, when he takes a drink from one his right hand is holding the cap on his head and the jar is in his left, but in the next shot the jar is in his right hand and the cap is in the left.
Continuity mistake: From the first time Boss Hogg appears on screen he has a goatee beard, apart from the scene towards the end in the courthouse when Uncle Jesse punches him.
Continuity mistake: When Cooter drives up to the police blockade with the flatbed extension, there is a wall of metal at the front of the "ramp" (the end closest to the cab). However, this soon changes to just a flat surface when it's the POV of the ramp from the car's perspective.
Continuity mistake: When Rosco arrives at Cooter's to pick up the General Lee he arrives with a tow truck. However, when Bo and Luke drive the General Lee out of Cooter's the tow truck that arrived with Rosco is gone.
Continuity mistake: When Bo is talking to Billy Prickett in the bar, Dil walks up behind Billy and rests his hands on his shoulders. In the next shot he has vanished and then is suddenly back again, with his arms back on Billy's shoulders.
Continuity mistake: While being chased by the police, Luke Duke grabs an arrow with an explosive tip and swings himself out the window to take a shot. He doesn't have a bow when he starts out the window, but he does when he is sitting fully on the window.
Continuity mistake: Towards the beginning, after Bow and Luke make there delivery to Laurie. Bow and Luke run away from Mr. Pullman(Laurie's Pa) and the brother. The son fires a shotgun at the Dukes from the right side of the truck and when he hits Mr. Pullman with gun, he fires, but the hole ends up on the left side of the car. Which is impossible with the angle he was shooting from.
Continuity mistake: When Luke and Bo are being chased in the beginning of the movie, a huge bullet hole is made in the left side of General Lee. Moments later it has vanished.
Continuity mistake: After the opening car chase, when General Lee is trapped between two vehicles, Bo hoists himself out the window, then Luke does the same after. But in the next exterior shot, they both are hoisting themselves out at the same time.
Continuity mistake: During the prison scene while Boss Hogg is talking to the Dukes some guy behind them in the cell keeps making fun of Boss. Boss Hogg finally pulls a hundred dollar bill out with his left hand and says he'll give it to whoever knocks that guy out. When the camera cuts behind Boss Hogg he is now holding it in his right hand, with no time to have changed hands.
Answer: It was never mentioned on the show but the producer/writer has stated they died in a car crash in public and on the DVD.