Continuity mistake: In the scene where Charlie and the snowman (his dad) are getting chased by the bullies, the sled gets split in half into two sled pieces. But you can clearly see that in some parts of this scene, Charlie is riding a real snowboard, and in others he is riding the half piece of sled.
Continuity mistake: In the scene where the Snowman is in the snow plough and he is facing the large amount of snow but when he is stuck to the snow he has turned in the opposite direction.
Continuity mistake: After Jack dies his son is making a snowman that later becomes his dad . You briefly see a scarf around the snowman. A little after that he puts the same scarf on the snowman.
Continuity mistake: When the van with hockey team members arrives at Charlie's house, there are two boys in the back seat and Natalie is standing behind them, outside the van. When Charlie gets into the back seat, Natalie is behind the driver and the two boys apparently have moved to the third row seats. However, when the van is driving away, the two boys are not visible and the third row seats are not occupied. (There is an image of an oval near the passenger window, perhaps to give the image of a boy there). (01:15:32 - 01:17:09)
Other mistake: When Natalie is standing outside of the hockey van near the driver's side passenger door, the side of the van below the window should be about to her shoulders but is only to her waist. The side is about one foot below the loop on the back of the driver's seat, but lines up with the loop after Natalie is seated in the van. (01:15:32 - 01:17:09)