Continuity mistake: Jane has the key in her hand, trying to unlock Peter Pan from the chains. But when Jane starts to fly, her hands spread out and the key disappears. Then she goes to free Peter Pan, and the key is back on her hand.
Continuity mistake: After Capt. Hook drops Jane into the water and Pan dives in to save her from the octopus, he begins to gloat. Looking at his scabbard there is no sword because he threw it at the mast to cut the rope. Next thing you know, the sword is back in the scabbard.
Continuity mistake: In the first movie Captain Hook totally blew up hangman's tree, the Lost Boys' and Peter Pan's hideout. But in this movie, the tree is exactly how it was before- even the same items inside.