Continuity mistake: In the opening scene, when the family is on their way to get a Christmas tree, they get into a road rage battle. If you look closely at the shape of the headlights, the car the family is in and the stunt car are noticeably different.
Continuity mistake: When Clark has the entire family outside to witness the lighting of the house, the positions of the in-laws change instantly from being clumped together to strung out in a line, depending on whether the shot is overhead or at ground level.
Continuity mistake: When Aunt Bethany asks "Do you hear it?", she leans forward in her chair. In the next shot she's suddenly sitting back, and leans forward again when she says, "It's a funny squeaky sound."
Continuity mistake: After Clark receives what he thinks is his bonus check, he says if there is enough money left over he will fly all of the relatives out to see the new pool. Everyone reacts with excitement, particularly Ellen, who is standing right next to Clark. She lets out a cry of excitement and raises her arms. The next shot is taken from the opposite point of view (from over Clark's shoulder). In this next shot, you can see everyone else still excited with the sudden exception of Ellen. She went from shrieking in excitement to having her mouth closed and her arms back down at her sides.
Continuity mistake: When Clark is going into the attic to hide presents, the ladder that smacks him in the face is a sliding ladder, but later when he is shut in the attic and uses the ladder to attract attention it is a folding ladder.
Revealing mistake: When Clark is on the sled, there's one frontal shot when the snow flies in the air before he touches it.
Continuity mistake: The christmas tree is visible from the dining room, but when Lewis goes beside it to smoke a cigar, you can't see him. When the tree is on fire, you don't see Lewis again and you can only see a branch of the tree.
Continuity mistake: When the squirrel jumps out of the tree and the whole family is hiding around the corner in the front entry, the camera alternates shots frequently from the front of the family to the back of the family. Each time the angle changes, Catherine's stance changes from her arm being around Russ to her arm at her side.
Continuity mistake: Less than a day after the ice breaks the neighbors' window, it has fixed itself in the outside shots as Clark is stuck in the attic.
Revealing mistake: When the neighbors fall onto the floor of their bedroom when Clark's Christmas lights finally go on, you can tell a stunt double is standing in for the female neighbor as she falls down at the foot of the bed.
Continuity mistake: When Clark falls off the roof, the staple gun goes down before him. In the next shot, it's not heading down from his point of view.
Revealing mistake: When Lewis's coat catches on fire after the Christmas tree explodes, the square on his coat that holds the "fire" is evident.
Other mistake: Up in the attic when Clark finds the videos, the video he watches is labelled Christmas '59 but while watching it, the sign being held up says "XMAS 1955"
Suggested correction: It may be a 2nd film he watched after the 1959 film. This may not be in real time, just like we only see Clark in the attic for a few min but in reality the family was gone assumingly much longer than we saw on film and Clark was there longer than we see.
Continuity mistake: When they first step up to the tree in the forest, Audrey is still moving. In the overhead shot, she stops, and we can see tracks in the snow where all four have been standing. The problem is, there are a lot of tracks. We're lead to believe they just walked up to the tree.
Continuity mistake: The retractable attic staircase is a type held closed only by light spring pressure, not a latch, but it doesn't budge when Clark jumps on it. When he initially opened it, and later when his wife does the same, it opens normally with a light tug from below on the cord.
Revealing mistake: When Clark notices that Lewis has caught on fire, he's only burning when he pushes him on the ground.
Visible crew/equipment: After the cat is electrocuted and begins smoking underneath the chair, the next camera angle still has the smoke machine in the shot next to the chair.
Continuity mistake: When the family is on the front lawn to inaugurate the Christmas lights, between shots a blue Lincoln at the curb disappears and a station wagon appears across the street.
Visible crew/equipment: When Eddie and Clark are putting the burned chair in the garbage, you can see the shadow of the camera following them.
Revealing mistake: When Julia Louis-Dreyfus has the dog jump on her, you can tell it's a stunt double. In the shot of Julia, the gem on the back of her sequence dress and her hair doesn't go below the gem. When Snot is about to jump on her, the hair completely covers the gem and is much fuller and looks like a wig.
