Wearing Panties in the Shower?
Watch the scene where Clark acts like Norman Bates in Psyco while Ellen is taking a shower. If you look at Ellen closely when clark throws open the shower curtain, you will notice that she still has her panties on in the shower!
Palm Trees in Chicago?
In the beginning of the film, as Clark and Rusty go to buy their new car, you notice palm trees in the back ground as they are talking to Eugene Levy. They are visible when they camera is showing Clark and Rusty and the street and other buildings are in the background. Not a problem except the Griswold's supposedly lived in Chicago.
Missing Tongue Girl
At the scene were the Griswolds get to Eddie's house, Clark asks a little girl how old she is. Eddie says she was born without a tongue, but if you look seconds before that you can clearly see her mouth is open and her tongue is sticking out.