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 the squirrel is being chased by Eddie's dog, it passes through the broken door and then vanishes. (01:22:07)
Character mistake: When the National Anthem is sung at the end the uniformed police officers should be at attention and saluting. The Lieutenant holding his hat over his heart is totally incorrect. Police and military in uniform keep their hats on, stand at attention and salute. It is correct for Eddie, as a veteran, to render a salute. It's kind of hard to hear, but it sounds like the 2 dads were arguing at breakfast about eating K rations, so one or both probably served in WW2. As vets, they should have also saluted, although it is not mandatory. For the uniformed on duty police it is. (01:32:53)
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.
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.
Continuity mistake: In the department store as Clark is talking with Mary, the lingerie sales lady, his left arm is supporting him on the glass counter as he is standing. The next shot when Rusty approaches, Clark is now bent down with his left arm resting on the counter.
Suggested correction: You actually see Clark go from sitting on the counter to bending down as the saleslady is modelling the undergarment.
That's not the part the mistake is talking about. The mistake is valid. Clark is sitting in the counter but is off screen when he changes position (so you don't actually see it). When Rusty enters the shot, Clark's hand is in the counter. In the next shot, his elbow is on the counter, with no time elapsing.
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: After the SWAT team busts into the Griswold's home and an officer yells "Freeze!", Clark's right arm changes position from either being raised or lowered as the scene quick cuts.
Continuity mistake: After Mr. Shirley tells Clark he will get a bonus plus twenty percent, Catherine, Rocky, and Ruby Sue cheer and get up from the couch to mingle with the relatives while Rusty and Audrey respond excitedly. There is a close up reaction shot of Clark as he begins falling, then a long shot of Clark falling to the floor as Catherine, Rocky, Ruby Sue, Audrey and Rusty are in their original positions on the couch, calmly watching Clark fall.
Revealing mistake: When Clark is outside at night rigging up the lights, it seems as though the moon is a little too large in the sky. (00:29:35)
Other mistake: After we see the cat pulling on the strand of white Christmas tree lights, there is a close up shot of the electrical outlet with one cord plugged into it. When the lights go off, both the colored and the white lights go out at the same time. Clark has to plug in two cords to make both sets of lights come back on. Either the colored lights should have been out to begin with, or both strands of lights should have come on with one plug. (01:09:05)
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 Todd, the snob neighbor, falls down the stairs, his wife Margot is not visible in the bedroom. (00:38:55)
Revealing mistake: When Clark falls from the top of his house, he grabs the gutter. It bends and a icicle is thrown from it to his neighbor's house. You can see the thread which guides it. (00:24:27)
Factual error: Prior to the cat being electrocuted, Clark is seen plugging the lights into a 110 volt outlet. However, when Rusty resets the breaker, it is a double pull breaker that is reset, which typically provides 220 volts, and the breaker is off instead of tripped. (01:09:00)
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.
