Continuity mistake: When the robber with the beard gets hit in the face with an iron, the iron hits him on the face, and leaves a mark slanted to the right. It also leaves a mark on his nose. When the two robbers are talking after they have been tricked and before Kevin puts the spider on one of the robbers, the iron mark is vertical and there is no mark on the nose anymore.
Visible crew/equipment: When Kevin is getting ready to light the firecrackers you can see a crew member's face reflected on the dishwasher.
Visible crew/equipment: When Marv is in the basement he closes the door behind him while he is getting ready to be hit by the iron you can see a crew member reflected on the basement door.
Visible crew/equipment: When Kevin is decorating the Christmas tree you can see a crew-member reflected in the Christmas bauble.
Revealing mistake: When talking to John Candy in the box van, the view outside the window screen is a projection, and the picture is not moving - at this point they're supposed to be driving.
Continuity mistake: When Kevin puts down his milk and snack on the table, he is looking at the presents under the tree. When he wakes up thinking his mom might be home and calling for her, when he goes in the room where the tree is, there are no presents.
Continuity mistake: When Marv and Harry first attempt to break into the McCallister's house, Harry tells Marv to go to the basement, and he goes to the front door. With the front steps covered in ice, Harry slips and falls down the steps, and his crowbar clanks down at the bottom of the first step. When Harry gets up and continues trying to get up the steps and into the house, the crowbar disappears - it is not in his hands.
Audio problem: When Kate is riding in the truck with the Kenosha Kickers playing "Deck the Halls", drums are heard. When the drums are not heard, the drummer is still seen drumming.
Continuity mistake: When Kevin is shooting toys off the laundry chute, his rifle is cocked by pushing forward on the slide, then pulling back. Later, when Kevin is shooting Marvin in the pet door, Kevin pulls back on the slide, then forwards to cock the gun.
Factual error: In the scene where Kevin swipes the toothbrush from the drugstore, he slides across a skating rink on his knees while being chased by the cop. Ice is slippery, but not THAT slippery (especially when it's been skated on). Kevin would have only slid a few feet before coming to a stop.
Visible crew/equipment: When Kevin's sleigh flies through the entrance door, the person riding it is an obvious stunt: Bulkier and way bigger than Kevin.
Continuity mistake: When Marv slips while walking down to the basement, he lands on the right side of the steps. When the angle changes, he is laying on the left side.
Revealing mistake: In the scene where Kevin goes to climb the shelves, we can see that the tarantula is fake as it doesn't move, nor would its legs be spread out if it was holding onto the side of the glass tank as shown.
Continuity mistake: When Kevin is dancing to 'Rocking Around the Christmas Tree' in the living room, the position of the record player is straight, but in the next shot it is halfway crooked.
Continuity mistake: When Kevin is shopping for groceries the paper towels are in the cart, but in the next shot the paper towels are on the conveyor belt.
Continuity mistake: When Kevin puts the food in the casher you can see a lot of people next to him, but in the next shot there's only one person behind him.
Revealing mistake: In the scene where John Candy and Catherine O'Hara are in the van and John Candy plays the clarinet, he never changes the positions of his fingers, but he plays a different note.
Suggested correction: He does move his fingers while playing his clarinet.
Continuity mistake: When Harry slips and somersaults down the Mccallister's iced front door steps for the second time, his hat falls off at the base of the stairs while he's tumbling, yet in the subsequent shot showing Harry, he is wearing his hat again.
Continuity mistake: When Mrs MacAllister is trying to get on the plane to Dallas, it is light in Paris. The movie cuts to evening scenes in Chicago. That cannot be. If it is evening in Chicago it is either night or very early morning in Paris - too early for it to be light. And when the plane takes off, it is darker than during check-in - showing that it is evening and not morning. December dusk in Paris is noon in Chicago.
Revealing mistake: When Marv is at the basement door trying to regain his stance, as he steps onto the icy ground, the "ice" bends and distorts the light just like a piece of plexiglass.
