Continuity mistake: During the horse and buggy ride to the church through downtown New York, when one of the girls is holding the reins by herself, you can tell there is a person under a red blanket at her feet (I guess to protect her while filming in case something goes wrong,) and only a moment later, the same blanket is black.
Continuity mistake: When the father goes out riding he hits his head on a tree branch. In the next scene, the wound is on the other side.
Other mistake: In the scene where Alyssa's father is in her room, she says "Ms. Kensington seems nice. Does she work with you?" Then she holds on to the bedpost and sort of swings herself around it while looking up at the ceiling with her tongue to one side of her mouth-she probably thought it was just a practice shot. She does the same thing in the scene where she is on the pottery wheel with Diane-she quickly looks up towards the camera.
Continuity mistake: In the scene where Diane is carrying Alyssa away from the Butkis's scrapyard, Alyssa has a hat on backwards, the camera cuts away and then cuts back to Alyssa and she has no hat on, then it cuts away again and in the next shot the hat appears again.
Continuity mistake: In the scene when Diane wants to introduce Amanda (Alyssa) to Roger, Amanda puts a hat on to cover her face and Carmen takes it off. Carmen first takes it off with her right hand but in the next shot which is in slow motion, she is taking it off with her left hand.
Plot hole: When Alyssa is playing football at the camp when everyone thinks she's Amanda and she has the ball she turns and starts running and yelling before the other teams start to even follow her.
Revealing mistake: When the twins first meet in the forest, they do so by running into each other then saying "I see me." Right before they crash into each other, they both put their arms up slightly to brace for the impact.
Continuity mistake: Amanda spits the snail into her left hand, but when she turns around it's in her right hand.
Plot hole: In the scene where Steve Guttenberg runs to the lake to wash off the mess from the food fight, Mary-Kate and Ashley Olsen come from their hiding place behind a canoe, to the canoe rack, where they can see whats going on without being seen. Kirstie Alley is still near the mess hall and she would have seen the girls.
Continuity mistake: Very early in the film, a street stickball game is interrupted by the arrival of a taxicab. As the cab approaches, it is a Chevrolet. As Diane and Amanda enter the cab and it starts to drive away, it is a Ford. As it continues to drive away, it is a Chevrolet again.
Continuity mistake: When the kids swap homes early in the film and the one in the orphanage is discovering "sloppy joes" the mess on her face goes from heaps to only a little.