The Great Bank Robbery - S4-E6
Revealing mistake: The bandits lock Bo and Luke inside closed coffins and then leave. Bo and Luke begin "rocking" the coffins back and forth to tip them over so they can escape. However in the following shots, as Luke is rocking inside his closed coffin, the camera slips or shifts too much, and you can see the barns' interior at the sides of the screen, alongside some equipment.
Revealing mistake: Bo and Luke Duke's car the "general Lee" usually has no glass in the side windows due the doors being welded shut as per NASCAR regulations which is why they climb through the windows to enter and leave the car, but when the general is doing one of its many jumps, in the long shots there is glass in the side windows.
The Ghost of General Lee - S2-E6
Revealing mistake: When you see Bo and Luke running around "naked", when they go to that girl's house to ask for clothes, while they are leaving you can see a little bit of the blue jeans that Bo was wearing to bring the naked effect to life.
Swamp Molly - S1-E6
Revealing mistake: When the truck goes into the water, you can see the driver was either a stunt driver or a dummy. Also, you can see the top of the truck just under the surface of the water, suggesting it was on the bottom. A few seconds later, and all you can see are bubbles.
Revealing mistake: When the boys are stopping to check the ambulance, you can see the smoke device burning used to simulate the engine running badly.
Revealing mistake: When spying on the hidden chop shop, the boys are using Cooter as a stepladder, with their feet on his shoulders. After he complains about their boots, they jump down after Daisy warns them. If you look at Cooter's shoulders, you can see that they're padded for the stunt.
Daisy's Song - S1-E2
Revealing mistake: As the Sheriff's cars are nearing the area where the Mobile Madam is, they're driving fast. As the RV and Bo are nearing the gate of the property they're on, you can see the two Sheriff's cars sitting just to the left of frame, then just beginning to move to make the pursuit look good.
Revealing mistake: Three times during the final chase there are close ups of the boys in the General Lee. If you look, the car is stationary on a brown dirt road, and the car is being shaken to simulate driving.
Revealing mistake: When there is a close up of the boys the first time they are driving through the junkyard, you can see through the passenger window that the car is being shaken to simulate driving.
Days of Shine and Roses - S2-E1
Revealing mistake: When watching the film in the beginning, one of the cops pursuing Jessie and Boss rolls over. As he does so, you can see the roll bars in the car, which accounts for the car not crushing.
Days of Shine and Roses - S2-E1
Revealing mistake: When "Spike" goes to pull the front fender of the car off, you can see the square outline of the spot meant for the spike.
Days of Shine and Roses - S2-E1
Revealing mistake: As Sheriff "Spike" Loomis goes to put the railroad spike into the car's door, there is a square outline of the spot set up for him to put the spike.
Revealing mistake: In the driver closeup shots, look at the backgrounds. A lot of the time, it shows the vehicle making turns, and the driver doesn't match the motion. Also, there are a lot of closeups where you see blue screen instead of scenery, or they go from city to country in a moment.
Revealing mistake: When Turk pushes Bo onto the tires, you can see his stunt double.
Revealing mistake: When the sheriff's cruiser is first seen, you can see Cooter's yellow cap. After the jump, you can see the black helmet of the stunt driver, and the patch of the Sheriff's office.
Gold Fever - S2-E2
Revealing mistake: Toward the beginning, when the Dukes meet the Texans, when the Texans toss up shot glasses to shoot, you see a white wire attached to one of them, probably to bust the glass on cue.
Answer: Various reasons, but mainly to drive the Dukes out of Hazzard County because the family have been foiling his schemes since his and Uncle Jesse's bootlegging days.
Captain Defenestrator