Factual error: When Clark is sliding on the saucer, he shoots out a shower of sparks when he crosses the street. Those old saucers were made of aluminum, and aluminum can't create sparks like other metal does.
Continuity mistake: When Clark is outside hanging the lights, he staples the sleeve of his shirt, under his wrist, to the eaves of the house. In the next shot, as he is pulling, the shirt is stapled over his wrist. (00:21:50)
Suggested correction: The position looks the same if you consider hand movement. Look at the opening of the sleeve and the hand position for comparison. I don't think this is an error.
Visible crew/equipment: When Ellen opens the door after Clark falls from the tree, there's a strange white thing visible for a few frames at the upper left of the door. Might be the hand of a crew member opening the door.
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.
Revealing mistake: When Clark and Eddie push the chair to see what happened, the burned cat is only visible in closeups. There's also a blue object next to the couch that look like an iron that is creating the smoke effect.
Continuity mistake: When Clark's neighbours return home, the man says to Clark, "Where do you think you're going to put a tree that big?" The trunk is very large, bigger then Clark's feet. Clark replies, "Bend over and I'll show you." Then Clark cuts the tree trunk - it is very thin and easy for him to cut.
Audio problem: During dinner on Christmas Eve there is a shot of the cat chewing on Christmas lights. The sound of the cat chewing is a fraction of a second off.
Other mistake: When Clark and Ellen are in bed talking, the People magazine cover Clark is holding does not have a date printed anywhere on it.
Continuity mistake: Todd and Margo are nearly two feet apart from each other as Margo suggests Todd slug Clark, but then they are much closer in the next shot when Margo leaves to perform the deed.
Continuity mistake: While Clark is having his difficult conversation with Mary, the department store counter girl, the knot on his tie alternates between being cinched tight to loose around his collar.
Continuity mistake: When Clark begins his rant about Mr. Shirley, Grandma Frances is directly behind Grandpa Art, with Rusty. The next shot of her and Rusty is almost standing next to Art.
Continuity mistake: Before Clark goes off on his rant about his boss, Grandma Frances places her hand on Rusty's shoulder, but the next shot has her hand on the side of Rusty's head.
Plot hole: When Bill and Clark are discussing the bonus delivery situation, it is December 21st, and Bill says his son received a delivery at his home via company courier. The bonus checks were to arrive to the employees before Christmas Eve, which would have given them plenty of time to contact each other that none of them got the bonus checks but did get enrollment in the Jelly of the Month Club.
Continuity mistake: The RV of Eddie is parked near the end of Clark's driveway by the large tree in the yard when Clark illuminates his house. When the family disperses and heads into the house, the overhead shot now shows the RV is parked up against the Griswold's garage door, far away from the edge of the driveway.
Continuity mistake: When Clark is stapling the lights to the roof, his leg is tangled in the sting of lights causing him to lose his balance and slide of the roof. As he slides/falls grabbing the gutter the string of lights around his leg disappears.
Factual error: The family is reacting to where Clark went flying down on his saucer, ending up in a Wal-Mart. With the speed and length of the trip, he would've been out of sight in seconds. There was no way that they could see him from where they were.
Continuity mistake: After Eddie's arrival Clark is on the lawn with "Snots." Clark's left had is shown as he is there alone with the dog trying to get his attention and his glove and wedding ring have both disappeared.
Visible crew/equipment: Just as Clark is about to smash through the hut on the greased up sled, the shadow of the camera is on the hut. (00:50:57)
Continuity mistake: When the grandfather is sleeping in the top of the bunk bed, there's a cheesecake poster on the ceiling. When Clark falls through the attic floor onto the bunk bed, it's not there.
Continuity mistake: The first time Clark fails with the lights, Ellen's mother says she hopes the kids see what a waste of resources it is. During this scene the level of her martini changes.
