Continuity mistake: When Henry is leaving the dock, Alexa waves with her right hand. Notice the watch. When Alexa grabs some butt from Doug, The watch is now on left arm.
Continuity mistake: When Drew is in her car at the restaurant, chastising Adam Sandler for faking not knowing how to read, a truck with the "Spam" logo drives by. The DVD commentary states the logo was added digitally later. When Adam's character runs back to his car, the logo is not on the truck anymore.
Continuity mistake: The dark roots of Lucy's hair can be seen off and on throughout the movie. One day she will have dark roots, and the next day she won't.
Continuity mistake: Lucy's lemon wedge appears out of nowhere and disappears a couple of times before Henry even uses it.
Continuity mistake: When Lucy watches the video tape for the first time, then goes outside and stands on the deck she turns to face Henry and her Dad. There are two small boats going toward each other just as they are about to pass the scene cuts back to Lucy, then you see the two about to pass each other again. This happens a total of three times.
Continuity mistake: During the scene where Ula is in the tank as Drew and Sandler begin to make love, Ula's necklace starts out outside his shirt. As the scene ends and he leaves, the necklace winds up underneath his shirt.
Continuity mistake: When Lucy is telling Henry about her diary, her hair moves from behind her ear to covering her ear between shots.
Continuity mistake: When Lucy and Henry are talking on the parking lot (just after he pretended to be illiterate), a boat with purple sail appears out of nowhere behind Henry and then disappears.
Plot hole: Lucy has been painting pictures of Henry since she moved into the institute. But she passes him at the zoo and doesn't recognize him.
Continuity mistake: Following their first encounter at the restaurant, Henry and Lucy are walking through the parking lot. The lighting conditions change from sunny to overcast between shots.
Continuity mistake: In the beginning, after Ula gets his stitches done, he starts to put on his vest when he goes over and talks to Henry. The shot cuts to Henry and then back to Ula and then he starts to put it on again.