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.
Factual error: After Allen and Madison jump into the water at the end of the movie and fend off the frogmen, they immediately come upon a coral reef and other aquatic features that appear tropical and which would not be found in the Hudson River/New York Harbor.
Factual error: When Allen falls into the water after Fat Jack's boat hits him, his wallet falls out of his pocket and rests on a coral reef. The ocean off Cape Cod is much too cold for coral reefs.
Other mistake: Joe Cirillo is credited as playing "Sergeant Munson", but his name badge in the movie reads "Edwards."
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.
Continuity mistake: While Allen is stuck in a traffic jam, several close-ups of Kornbluth show a yellow cab next to him. In the wide angles the car swaps to a dark coloured private vehicle.
Continuity mistake: When Allen is fighting with Kornbluth at the dentist, the position of the large lamp in the background changes between shots.
Continuity mistake: Freddie leaves the Penthouse magazine on a counter, where a woman behind picks it up. In the next shot, she picks it up again.
Continuity mistake: At the wedding, Freddie throws coins on the floor and Allen scolds him. The position of the kids and adults behind keeps changing drastically between shots.
Continuity mistake: When Hanks sneaks Madison out of the lab, his right arm is close to her chest, covered by a grey cloth. When the angle changes the arm is uncovered.
Continuity mistake: When Allen is brought home blindfolded and is interviewed by the press, two journalists without a camera approach from behind. In the front angle, a split second later, a TV camera appears out of nowhere.
Continuity mistake: The position of the dentist's tools on the tray changes between angles.
