Luther Krank sees the advertisement of a Carnival Ship then books passage on what he refers as the luxury ship Jubilee. The Carnival Jubilee was one of Carnival's smaller "Holiday" class ships that first sailed in 1986. Shortly before this movie was made, the Jubilee was transferred to P & O lines of Australia and became the Pacific Sun. There is no way Luther could have sailed on the Jubilee in Christmas of '04.
Luther Krank states that he has spent six weeks planning the cruise when in fact he got the idea the day after Thanksgiving, the day he took Blair to the airport. Though we all may wish for more time between Thanksgiving and Christmas, there has never been "six weeks" between them.
The front of the Krank house changes at one point of the movie. Normally, the bay window is on the left side of the house and the door knob on the front door is on the right side of the door. In the scene after Luther has iced his front walkway, when the mailman is walking across his yard, the bay window is on the right side of the house and the door knob is on the left side of the front door. Strangely enough, the house number still reads 1482 correctly.
When Marty arrives for the party, he brings the only can of ham, and Nora serves it, happy that she was able to serve Blair's favorite. Then later, Luther sees the full can of ham and brings it over to the neighbors.
When Nora is trying to leave her house and Vic grabs her window she rolls it up to try to get rid of him. His fingers get stuck and Nora does not roll it back down, however in one shot the window is back down then in the next shot it is up again
When Luther refuses to buy the Christmas tree from the Boy Scouts, Nora and Luther go in the front door which has a Christmas wreath on it. The Boy Scout leader complains to a group of neighbors and they all turn to look at the Kranks' house. When the door is seen from across the street and in a series of close-ups, the door has no wreath on it. The wreath reappears and stays there until Luther throws it aside.
Nora, at lunch with Candi and Merry, reveals that the Kranks are avoiding Christmas and that there will be no Christmas Eve party. Candi asks the question "When do you leave?". Nora had not mentioned the cruise.
When the Power Lineman restores power to the Kranks' house, he is shown touching hi-power lines wearing only leather gloves. He also "hammers" on the side of the transformer. He would have been immediately electrocuted.
The goof items below may give away important plot points.
During the Christmas party, when Marty and Enrique started to perform a song in Spanish, behind Marty was someone playing the Andean pan-pipe (an instrument with two rows on bamboo pipes arranged in size order). He is playing the instrument backwards, the smaller row must be facing him not away from him.
When the police bring Blair and Enrique to the party, they are shown getting out of the back seat of the police car. When you next see the police car, the criminal is shown handcuffed in the back seat as well.