Continuity mistake: At the end of the movie, before the Guardians leave, Jamie rushes over to hug Jack. In the first shot, the top of his head nearly reaches Jack's ribcage. However, in the following close-up shot, Jamie is almost at the same height as Jack's shoulders. (01:27:30)
Revealing mistake: During Jack's memories, when he is holding the antlers up to his head, Jack's sister's boot can be seen coming through the fabric of her dress.