Continuity mistake: After the Grinch unscrews the light bulb in the town Christmas tree, all the lights in the town go dark and the Grinch starts to take off in his sled-thing. When they show a close up of him, the lights are on. Then a few seconds later, the lights are off again.
Continuity mistake: When Mrs. Lopez calls Allie out as she is working on her illuminated manuscript, the object of her attention drops the pen before turning around. In the next shot he's holding the same pen in hand. (00:04:55)