Continuity mistake: When Laurie sees Amy painting in Europe, in his closeup he takes the cigarette out of his mouth and throws it on the ground. But in the next shot, with Amy in the foreground, as Laurie is walking towards her in the background, notice how he, once again, removes the cigarette from his mouth and throws it on the ground.
Continuity mistake: When Amy is struck by her teacher and Marmee writes Mr. Davis a letter chastising him, when Jo says inappropriate things about Mr. Davis, Marmee assigns Amy's education to Jo. When the camera shows Jo's reaction, behind her you can see Amy sighing and slumping in disappointment, and then the camera cuts to show Amy doing the same exact thing again.
Other mistake: When Beth visits the Hummel's house, the Hummel baby is supposedly crying because he is sick. In reality, the Hummel baby is crying because the Hummel mother accidentally bends back the baby's foot, when she hands the potato that Beth gives her, to one of the Hummel daughters.
Continuity mistake: When Friedrich talks to Jo in the hallway about her novel, you hear the footsteps of a man coming, and you see him stop right behind Friedrich. The camera cuts briefly to Jo, then back to Friedrich, and the man is gone. Given the acoustics of the hallway he had no chance to walk off secretly.
Revealing mistake: When Amy comes back home from Europe she gives her parents one of her paintings as a gift. It is wrapped in lace, but in the close-up of the unwrapping, when the ribbon is removed, you see that the lace is only on top, covering the painting, not wrapped around as it's supposed to be.