When Evian goes to Skye's house and his mother opens the door, there is a baby in a Johnny-Jump-Up (one of those things that hangs in a door frame that the baby can jump up and down in) surrounded by people directly visible behind Skye's mother. The camera cuts to Evian, and when it cuts back to Mrs. Corrigan, the baby and the people are no longer there.
The table behind the practicing dancing group is flattened by Mary Katherine Gallagher, but then in the next scene the table is perfect.
In the beginning sequence, young Mary takes off her sandals. The next time they show her she has them on again, and then when they show her jumping into the water they're off again.
When Mary is licking the stop-sign, a lime Volkswagen drives by. A short while later, the same lime Volkswage is seen several times in different shots, either driving or parked. * The green Volkswagen Bug repeatedly seen in outside shots isn't one car driving around. All cars used in the movie were Volkswagen Bugs.
After the paint is dumped on Mary during the talent contest auditions, she starts running, going through the audience, turning right down the hall then turning another right to run outside through the large front doors. Father Ritley pursues her down the long hall - followed closely, then being passed by, a fast running boy from the crowd. However, when the Priest arrives at the front door, he is alone, and the boy is nowhere to be seen, neither having run past the main doorway to continue down the hall, or following Father Ritley to the doorway to watch as Mary rides away with Slater on his motorcycle.
When Mary's grandmother is in the principals office the principal refers to her grandmother as Mrs. Gallagher, but later on we learn that she is the mother of Mary's mother. Her last name would only be Gallagher if she was the mother of Mary's father, not her mother.
Grandma (Glynnis Johns) tells Mary that she danced in Gypsy on Broadway, two shows a day, six days a week. Gypsy would only have played eight shows a week, especially with Ethel Merman as the star. She never would have agreed to twelve performances a week.
When Mary is describing her ugly house, yard and dog, it is all shown in the past so, obviously the dog is shown as a puppy. When the story is in the present the puppy is replaced with an older dog to show it has aged.
In one scene when Mary is talking to her friend in front of the school, The friend is spinning a basketball in her hand. When she puts it in her other hand you can see the device that spins the ball.
When the TV tips over on top of the dog, the shot is flipped on the vertical axis, making the weatherman appear to be upside down (closer examination also shows the map is backward and the TV brand logo is on the wrong side).
Mary's grandmother is clearly not playing the piano music we hear. She is also not playing the drums.
In the scene were Mary Katherine is praying to God while the Vicks Vapor is running, she makes the sign of the cross backwards. She touches her right shoulder first instead of touching her left shoulder first. Roman Catholics make the sign of the cross touching their left shoulder first, and then their right shoulder secondly.
In one scene, Mary is giving the sign of the cross with her left hand, not her right which is correct.