Revealing mistake: When Crewe dumps the car in the river, you can see the wire attached to it that was used to pull it out of the water. Burt Reynolds mentions it on the DVD commentary.
Revealing mistake: When Helga is sent flying into her room, the support cable that is attached to her is visible.
Revealing mistake: When Mongo wakes up and breaks free of the chains, in the shot where he breaks free, the chains suddenly shift position and some even disappear. This is because the camera was stopped and the chains were replaced with fake break always before the camera was restarted. Another way to see this is because the water that dripping down Mongo's face suddenly stops. (01:02:15)
Revealing mistake: When Pinback is hanging from the lift, just before he decides to undo the bolts, you can see a piece of wood supporting his back. (00:43:00)
Revealing mistake: When Clint Eastwood and Jeff Bridges are being chased by George Kennedy and his partner, Bridges is driving off the dirt road down and embankment and you can clearly see that in the passenger seat is a faceless dummy instead of Eastwood or another stunt man.
Revealing mistake: When Herbie dives into the ocean, water can be seen coming out of the open back window, even though the next shot shows the inside completely dry and the window closed.
Revealing mistake: Whilst being followed by Celine, Julie walks up a small flight of steps. When this happens, a blue car can be seen turning around a corner and driving past the camera. Just as Julie walks into frame, the driver of the blue car can be seen looking at the camera just as he drives past it. (00:05:58)