Revealing mistake: During the scene when Audrey is having a nightmare about eating too much while on vacation, the nightmare ends with her inflating like a balloon from all the food. Her blouse splits open and down the middle, where the buttons have broken, the dark balloon used for the effect is visible.
Audio problem: In the beginning of the movie when Clark is preparing to light the Bar-B-Q, He squirts charcoal fluid out of a plastic bottle. Then Ellen squirts more fluid onto the coals out of the same plastic bottle. Listen to the sound; it is the distinctive sound of a metal charcoal lighter fluid bottle.
Question: In the opening credits, Clark's passport has the name "Clark W Griswald" instead of Griswold. Was this just intended because Clark can never seem to do anything right, or even get it fixed when it's wrong? (like the Wagon Queen Family Truckster he ended up buying even though that's not the car he ordered...?).