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.
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.
In the scene where Mary is kissing a stop sign with the biker watching her from across the street, a green VW Bug can be seen behind her as she walks away. The car drives back and forth throughout the shot and is also seen parked behind the motorcycle rider,and then again in the very next shot again driving back and forth.
Backstage before Mary's group performs, Helen is wearing her "feat-of-strength" green costume. A few minutes later, she is seen wearing her school uniform, and then she is back in the green costume in the next shot.
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.
In the video shop after the _Armageddon (1998)_ spoof, the man asks
Mary if she's rewound the tape, and she puts it in a box and gives it him, but in the next shot, his hand is holding an unboxed tape.
When Mary gets on Slater's bike, it is just after having paint tipped on her, which is all down her front, and she is leaning into him when they are riding, yet when they get off, he has no paint on the back of his jacket.
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.
Throughout the movie, it shows Mary kneeling at her bed praying at night. The nightstand is always on her right. However, in the one scene where she kisses the picture of her parents and blows out the candle right before "Jesus" comes into her room, the nightstand is on her left.
The grandmother is wearing a green outfit and playing the piano while Mary is trying to dance at her house to practice for the talent show. Cut to a different day, a close up on the grandmother's hands playing the piano. She's still wearing the green outfit. The camera pulls back to show the Special Ed class trying to dance. The Grandmother is wearing a blue outfit.
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.
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.