When the Homecomming candidates are making their speeches the camera is showing close ups of Lisa while the 4H girl makes her speech. In the long shot, there is an empty chair, but in the close-up there is someone in the chair.
When the girls are in the doctor's office for Diane's ultrasound, one of the girls starts moving the wand over Diane's belly, looking at the images on the screen. There is no conducting jelly on Diane, so there should be nothing showing up on the screen.
When Jack is racing for the end zone during the football game, the camera cuts to the clock counting down as if he is "racing" to get to the goal line before the clock hits zero. In a movie that was supposed to have so much to do with football/cheerleading, it's amazing that the writer/director didn't realize that since the play started during regulation, it wouldn't matter if Jack crossed the goal line with 0:00 on the clock; however, the scene is shot as if when the clock hits 0:00 and Jack was short of the end zone, the play would end.