National Lampoon's Christmas Vacation (1989)

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

Revealing mistake: When Clark notices that Lewis has caught on fire, he's only burning when he pushes him on the ground.

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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.

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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.

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Continuity mistake: When Clarke is installing the Christmas lights, the rope on the ladder keeps appearing and disappearing.

00:23:00

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.

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Continuity 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 Clark sees the lights go out, he sees 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

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.

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Revealing mistake: The Christmas tree is still visible after it has burnt down.

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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.

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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: At the beginning of the movie, despite the fact that Clark hits the accelerator and the car goes really fast, the background shows the car is going at a normal speed.

00:04:45

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

Audio problem: When Ellen cuts a head of cabbage in half after her mother asks her if she's smoking again, the sound of the knife hitting the cutting board is heard before the knife hits the cabbage.

00:23:15

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.

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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.

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Continuity mistake: When Eddie and Clark are drinking eggnog, Eddie knocks down the decoration with propellers on it. When Eddie walks to the table with the nuts on it the camera shots cut from Eddie to Clark attempting to fix the decoration. In each shot that we go back to Clark, the number of propellers left on the decoration change even after Clark has given up fixing it.

00:45:55

Other mistake: When Clarke and Eddy are drinking eggnog by the tree, and Snots is drinking the tree water, look at the tree's trunk. It's a birch tree not a pine.

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Continuity mistake: The blinds are ripped out of the neighbors' window frame when Clark "harvests" his replacement tree from outside. However, when Margot is outside telling Todd to "slug that creep in the face", you can see blinds are still in the window.

01:17:20 - 01:21:55