Continuity mistake: When out at a pub, Allen finds himself laying on the bar, and his brother Freddie starts to talk to him. Between shots Freddies glass goes from being on the bar to in his hand. (00:13:15)
Continuity mistake: When at the bar, Allen makes a woman spill drink on her dress, and she walks off. Between shots the bartender picks up her glass and starts to wipe the table twice. (00:14:45)
Continuity mistake: When Tom Hanks is in the dinghy by himself, the outboard motor has no cover. He falls into the water and the dinghy circles him several times. One of the shots shows the motor with its cover in place. (It is an Evinrude motor). (00:22:15)
Continuity mistake: When Allen and Madison are walking along, they pass a preztel stand, and you can see a woman walk past the stand and look at it. In the next shot there is nobody at the pretzel stand. (00:43:50)
Suggested correction: You see the woman walking along just past the pretzel stand and beyond as the camera pans up.
Continuity mistake: When Madison is taking a bath, she dips her head right under the water. Then when she gets out, her hair is soaking, but in seconds, her hair becomes very dry. (00:46:50 - 00:48:30)
Continuity mistake: The Vista logo on Allen's credit card disappears.
Continuity mistake: When Tom Hanks stabs Eugene Levy with a needle in the dentist's office, Levy is not wearing a bib. When Levy sits in the chair, he has a bib on. Then when he gets up, the bib is gone.
Continuity mistake: When Allen tells his secretary that his father passed away, she is either holding the note from the side or from the top, depending on the angle.
Continuity mistake: When the mermaid rescues Allen after the boating accident, the amount of sand on Allen's face changes from the whole side of his face to just his chin to hardly any sand at all. This goes on for the whole scene.
Continuity mistake: When Madison is taking a bath in Allen's apartment, she starts the water and then as the camera pans around her, all of a sudden the big tub is full.
Continuity mistake: When Madison runs from the ice-skating she is barefoot. In the next shots she magically has managed to bring her shoes and has put them on.
Suggested correction: Right before Madison rushes away from the ice rink (01:10:10), she grabs her ballerina flats, and when she runs away from Allen, she's barefoot while holding the flats in her left hand. Then, the skate rental guy tackles Allen. When it cuts to Madison in the shot facing her back, she's still running barefoot while holding the flats in her right hand.
Continuity mistake: Before Allen jumps to chase the mermaid, the helicopter is above him and he looks up. His hair doesn't move despite the rotors above. Then in the following shots it finally does move.
Continuity mistake: When the army exits the lab to find the mermaid the pavement is wet and the sky is cloudy. The following aerial shot shows the pavement dry and the light sunny. The light keeps changing with no continuity throughout the scene: cloudy, sunny, dawn, dusk.
Continuity mistake: When Madison leaves Allen's apartment to go to Bloomingdales the tie she is wearing is plain navy blue, when she arrives at the store it has changed to blue with diagonal red stripes.
Continuity mistake: When Walter soaks Madison she falls forward towards the curb. In the close-up a flowerpot appears, which disappears in the wide angle, where she lies 45ยบ to the left of the curb.
Continuity mistake: Allen arrives to the market dancing and juggling potatoes. Behind Freddie there's a man scratching his nose. In the next shot his hand is down and he is raising it to scratch his nose again.
Continuity mistake: Hanks puts Madison inside the car where the solar roof is open. When he starts the car, half a second later, the roof is closed.
Continuity mistake: Allen drives through a spotless park, but, when the angle cuts, a flock of pigeons appears ahead.
Continuity mistake: When Freddie, as a kid, is in the boat throwing the coins, a man in the background on the left side appears several meters to the right in the next shot. The second time he throws the coins, a guy next to the flag disappears between shots.
Continuity mistake: Before Allen asks his secretary if anybody called, she holds a yellow paper at chest level. Half a second later, when the angle changes, the paper is down and she is raising it again.