The tanning bed employee's hair and outfit change between when Nora and Luther arrive and when Nora is looking for a band-aid.
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 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.
The cut on Nora Krank's forehead she received while tanning, and the position of her fringe, change and disappear between shots.
At the tanning salon in the mall, where Luther and Nora attempt to get a tan, Nora in the process gets interrupted and hits her forehead on the device, causing her to get a fairly good sized cut there, thereby making her bleed enough to force her to go out to the front to get a band-aid. The cut and bleeding on her forehead is existent throughout that whole part of the scene. But following this scene, for the rest of the movie, her forehead never shows any band-aid, scab, or any indication that she was ever just recently hurt there.
Luther comes out of the tanning bed with a dark tan after only a few minutes. Achieving that kind of tan from a winter-white complexion takes weeks of sessions.
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 not have been immediately electrocuted as described because he is insulated.
At the beginning of the film Lester says that Blair is flying out on the Sunday after Thanksgiving. Lester gets the idea for the cruise on the journey home. At the party on Christmas Eve, Lester says he had been planning for six weeks whereas it had actually only been a month.
The radio that Spike uses to contact the police to have them delay from the airport is an HF radio, used by amateur radio operators, and is not able to transmit (and is not allowed) on the police bands.
The Scouts selling the trees are supposed to be Boy Scouts, as evidenced by the Troop 18 sign and the Camporee reference, but the Scouts selling the trees are wearing Cub Scout uniforms.
Blair mentions that Enrique has never seen a white Christmas, not that he's never seen snow. Since college kids almost always go home during Christmas time, he likely has spent all his Christmases in Peru, not Rhode Island.
Marty, is at the Kranks' Xmas party in ordinary clothes, but when he leaves he's got a Santa suit on.
When Nora Krank is chasing the canned ham in the parking lot at the grocery, there are trees with leaves visible in the background, showing that the scene was not filmed in December.
When the two kids playing the video game get up, they drop the controllers but the game keeps running as if they are playing.
When Luther returns home from picking up the Christmas tree, he pulls it off the roof of his car without unhooking it in any way, clearly revealing the Christmas tree was not attached to the car as it would have been since he was driving with it on the roof.
When Luther is on the roof with Frosty, he is pulling him face down. However, in the next shot, Frosty is face up.
When the carolers come up the walk and slip on the ice that Luther made, you can see the ice flex when they land, showing that it is a flimsy platform on top of the ground.
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.
While Luther hangs from the rope outside his house, the firefighter behind Vic is hit in the head with the ladder that they raising.
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.
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.
When the firefighters arrive at the Krank home to help Luther get untangled from the power cords, they pull a ladder off the fire truck. In the process, the firefighter in the back gets hit in the head with the ladder. The actor portraying the firefighter is clearly surprised by this, but otherwise stays in character and continues the scene.
When Luther writes the letter to his office, he makes the second word in the intro (colleagues) begin with a lowercase letter. The formal manner is to capitalize each noun in a salutation.