Continuity mistake: In the Hoover Dam scene, the tour group is walking through an underground tunnel when Clark messes with the wall and more water than normal starts coming out. He gets gum from Audrey and starts plugging the holes. He puts gum on the first hole and when the gum makes a bubble filling with water, he puts another chewed piece on the bubble. In the next shot, there is no piece on the bubble and he puts a chewed piece on another hole in the wall.
Factual error: On Marty the blackjack dealer's name tag, his hometown is spelled out 'Masellon, OH'. It should be 'Massillon'. (00:56:10)
Other mistake: In this film, the oldest son of Catherine and Eddie is named Denny. In the original film, his name was Dale. He looks the same (although a different actor used) so it's under the assumption it's the same kid.
Continuity mistake: When Clark and Ellen are on the plane and go to the restroom to join the mile high club. Ellen goes to the back of the plane while Clark goes to the front.
Other mistake: When Rusty put coins into the slot machine to win the first car, he only put in 2 coins, but if you look closely at the payout table, he would have had to put in 3 coins to win the car. The same thing happened when he won the Viper. Also, when he won the Viper, the light on the top of the slot machine did not flash on and off, which would have happened if he had any type of big win.