When the little boy goes in to talk to Jack Nickelson in his bedroom, the little boy sits in his lap. Jack puts his hand on his son's shoulder. Then they switch to the mirror showing them, and his hand is still on his shoulder. But then when they go back to Jack and his son (not the reflection of them in the mirror) Jack's hand is no where near his son's shoulder (and they switched scenes just like *that*!) Either that's a slip up, or he's REALLY fast!