Continuity mistake: When Hodaka first fires his gun whilst being threatened by the man, the shell casing lands on the ground beside him, right next to his head. A couple seconds later, when Hina goes to help him up so they can run off together, the shell casing has vanished from the ground. (00:22:06)
Continuity mistake: When Santa tells Noelle he's anxious about inheriting his dad's role, the position of his arms is inconsistent between front and side shots.
Continuity mistake: When in the train the cats sing "bothered by mice" the cat in the sink changes positions between shots.
Continuity mistake: The clocks are not coordinated, affecting the time frame. Josh and Jen are decorating the Christmas tree at 8:08 PM. Josh goes to his room, "past his bedtime." Josh writes his list for Santa. At 7:15, Josh hears a car drive up, so he looks out the window. Dad meets mom in the driveway and says, "It's almost midnight." (00:05:29 - 00:07:58)
Continuity mistake: After the alien abduction, Emmet plans to lead a rescue mission and opens the gate asking "Who's coming with me?" During the sequence, the shadows change completely. At first he is not casting much of a shadow, then it reaches the metal doors, then it stops midway towards it. (00:20:55)