When the Squirrel Lady gives Vera and Merrill directions, she says, "Go 5.4 miles and you'll see a yellow sign with some graffiti on it...". When they see the sign, Merrill says, "We're at 2.4 miles exactly!" which is incorrect.
When Tracy and Nick are discussing travel plans in the restaurant, Nick says they are 3 hours ahead of everyone else since they took the helicopter. This is impossible considering Tracy went north (away from Silver City, New Mexico) to check in with her boyfriend in the previous scene.
When we first see Enrico on the train, he seems to be sitting facing in the direction that the train is traveling (judging by the direction in which he is turning his head to look at the passing scenery). In the next shot, from inside the train, we see that he is sitting in a seat facing away from the direction the train is traveling.
As Blaine is climbing the tower trying to outrun the truck, the rope pulling the truck changes position (relative to him) several times. Sometimes it's behind him, sometimes in front, sometimes to his left, sometimes to his right.
Tracey throws several objects at the truck when she discovers her boyfriend cheating, denting the hood in several places. A few minutes later, when she is chasing the truck through the brush, the dents are gone.
When Mr. Sinclair calls to have his other Lear Jet ready for use, the next shot is a Gulfstream G-4 with five well spaced large oval windows. But the interior shots are of a much larger passenger jet with multiple small windows and massive headroom.
As Duane Cody hangs from the rope of the hot air balloon, he crashes into a herd of cows. The rope is originally wrapped around his arm twice but in subsequent shots it switches randomly from being wrapped twice to once or not at all until he falls off the rope.
When Blaine sticks out his tongue at the girl when he's driving, his tongue has healed and there isn't a huge bruise, as there was before. If this all took place in one day, this certainly could not have happened, as it would not have healed completely.
In the DVD they tell us that a stunt driver was driving the car when Duane grabbed the rope of the hot air balloon. You can see the driver through the plastic window made in the seat. Also the seat sits out further than the passenger seat.
The bullet that was fired and travels next to the rocket car defies the laws of physics. Assuming that the bullet was fired parallel to the ground, the bullet should remain in the air for the same length of time as it would take to drop the bullet from the same height. The bullet in this scene remained in the air for a much longer period of time.
Immediately after Vera and Merrill first meet, Merrill receives a phone call where she states that some merchandise must ship immediately to get in stores by Mother's Day. Since Mother's Day in the USA always falls in mid-May, we should conclude that this film takes place in April (or possibly early May). Yet this is inconsistent with the fact that Owen had refereed a NFL game just one week earlier, since the superbowl occurs at the end of January, and pre-season play does not start up until August.
As Duane and the jeep are being pulled up the radar tower, just when the front wheels are in the air we can see a lot of dust coming from the right-back side of it but the rear wheels are not turning in reverse.
When the truck gets stuck at the top of the tower, the rope coming off of the radar is shown slack. With the tension caused by the weight of the truck and rotation of the radar, the rope should be taut.
Just before the radar breaks loose from the tower there is a close-up of the rope wound around the radar. You can clearly see the rope fastened to the base of the radar ABOVE the coiled rope. There may even be two separate ropes, as the coil looks loosely wound, which wouldn't be the case if it had pulled the weight of the truck up the tower.
When the Pear family is driving the Hitlermobile, Jon Lovitz is shown fiddling with the cigarette lighter. Shortly after he drops it, the camera cuts briefly to a shot of the driver's side front wheel as the car runs over an object. The object is the muffler that Zach and Enrico hit with the van earlier, and the junk truck that dropped it can be seen ahead of the car. This is impossible given the elapsed time since that first encounter. Furthermore, the side of the vehicle is not that of the Hitlermobile, but something newer (wrong color and contours; it is probably Zach's van).