Continuity mistake: In the scene in Central Park as Santa speaks with Michael, Santa's arm is either on the book of Christmas lists, or off it, as the scenes switch between looking over Michael's shoulder and over Santa's shoulder.
Continuity mistake: After Sarah has called at Harry's office, Harry prepares to open his office door to see her out. The camera cuts back to Sarah for a moment, then back to the camera angle on Harry as she walks to the door. In that short space of time, the sliding cupboard doors have changed their configuration, and the blinds in the upper left of the frame have partially closed. (00:18:45)
Continuity mistake: When Willie is in bed and the kid comes in with the Christmas countdown candy box he gets in bed with Willie. Willie's robe keeps changing from being open to being closed.