Revealing mistake: In one scene, when Jack is in the dungeon talking to the fairy, you can clearly see that the "fairy" is nothing more than a light on a thin piece of wire. The wire can be seen quite clearly for two shots.
Revealing mistake: When Gary and Wyatt come home and see Chet turned into a pile of poo, Chet shoots his tongue from his mouth and catches a fly. Look closely, the tongue flies completely out of his mouth and is attached to a metal spring. (01:24:55)
Revealing mistake: During the barn raise you see the some men using ridiculously small nails to connect huge beams. (01:20:20)
Revealing mistake: When Philippe the Mouse is caught by the Bishop's guards after he has escaped from prison, Navarre shoots an arrow into one of the guard's arms to stop him cutting Philippe's throat. If you look at the spot on the guard's upper arm where the arrow will hit just as Philippe says 'May God have mercy on my soul', you will see that there is already a hole there - even before the arrow hits him.
Revealing mistake: When Lane becomes depressed he goes out to the garage and ties a red cord around his neck and to the ceiling to hang himself. He thinks better of it, but his mother opens the door and knocks him off the steps and he hangs by the cord. If you look closely you can see that there is no cord hung around his neck, he merely holds his hand up and mimics grabbing the cord around his neck. The cord seems to be attached to something on his back. (00:15:40)
Revealing mistake: When Jack and Joan escape in the F16, if you look at the back wheels, you can see the car driveshafts that drive the wheels. Jet aircraft don't have driveshafts.
Revealing mistake: When Kent rolls out of the front door with the popcorn, it is obviously a stunt double due to the man's hair being brown/black and Kent having blonde hair. (01:38:25)
Revealing mistake: When Cay and Vivian are out in the desert it starts raining. Yet once they're in the car after the big kiss they seem completely dry with their hair only slightly damp. Clearly they just got their hair sprayed.