Continuity mistake: After Marv falls out the window during the kidnap rehearsal, the bottom part of the window falls out along with Marv. However, after Kevin walks in, there is an extra pane left on the right side of the window. And after that, when the camera switches to the outside, the window is all crooked and bent, but it wasn't in the previous scenes.
Revealing mistake: In the scene where the kid sneaks into the butler's private quarters and sits in his chair, the butler sneaks up behind him and scares the kid. When he is sneaking up behind him, the camera shot is supposed to be the butler's point of view, but you can easily tell it isn't really. Watch closely as the camera goes right over the coffee table without making any noise, or without moving the camera.
Continuity mistake: In the flood scene when Natalie walks in and begins to scream, Kevin is standing on the first step of the stairs with his shirt uneven, and the strings for his pants are showing. In the next shot, Kevins clothes are neatly ironed, his shirt is even, and the strings have disappeared. (00:28:30)Reservoir Dog
Continuity mistake: After Natalie arrives back at the house to find her mansion has been flooded, she screams and says "what?" six times. At that time, there is a shot of a purple shampoo bottle and a rubber ducky just in front of the stairs. Then Kevin says "I know it looks bad but." and during that line you can see that the shampoo bottle and rubber duck is about 10 meters from where it was before. It couldn't have floated that far in a few seconds.
Continuity mistake: On Christmas morning, Kevin fiddles with the presents. When his father says he has to go and pick up the royal family, look at the presents over Kevin's shoulder. The view changes so it is by the Christmas tree, and the same presents are in a different position (especially the dark metallic green one and stripy one).
Audio problem: When the police are taking Marv and Vera away, they have a little argument about what prison is like etc, though they are arguing quite loudly, Marv's lips don't move at all, and Vera is still chewing gum.
Continuity mistake: When Kevin gets told off for the second time for causing a scene at the party, he goes to his room and lays on the bed. The teddy bear is lying between the pillows on its side. A closer shot is shown, and the teddy bear is sitting upright.
Visible crew/equipment: When Natalie, Kevin, and his father are trimming the tree, the camera shows a shot of Natalie pulling a thick red rope-like tree decoration. Watch closely as the shot moves closer to Natalie and you'll see a lovely shadow of the camera person.
Continuity mistake: When Kevin escapes from the wine cellar using the dumbwaiter, he goes up. Then, he sends it down onto the robber's head. Then, the female sends it up, and then back down again when it hits the male robber's hand. But, when Prescot goes to the dumbwaiter chute, the dumbwaiter is up instead of down.
Visible crew/equipment: When Molly walks out with Kevin after he gets caught by Prescott in his room, Kevin explains why he thinks Prescott's the inside man. Then, while they are talking at the door, the tip of the cameraman's finger is visible on the very top left hand corner of the shot. It also appears several times in other shots during the conversation until Molly walks away.
Continuity mistake: When Kevin puts the phone down after calling his Mum he says oh great, but then it switches to a different shot and his facial expression and posture is different. there was not enough time for him to change and it doesn't flow on well.
Other mistake: As Vera is trying to get into the room where Marv is, Kevin is playing insults with Marv's voice loud enough for Vera to hear through the door. She enters the room and Marv is oblivious to why she's angry at him as if he didn't hear the playback, despite being in the room as they were played in.