Natalie's clothes abruptly appear on her when she runs out of the bathroom after undressing to take a bath.
At the hospital, automatic doors open for Zack and Natalie even though it's been established that they're invisible.
When Natalie, Zach, and Tommy are at the gas station, a collection jar with a sign that says "Please Help Find Stewart Fund" is attached to the pillar holding up the cigarette rack. When they leave, the jar and sign are attached to the cash register on the opposite side of the counter.
Since many people in emergency situations can't talk, 911 operators don't hang up if there is no answer on the other end. The operator stays on the line to trace the call, dispatch emergency vehicles, and await any possible changes.
At the very beginning when Brad picks up Zach at his house, the cameraman is reflected in the rearview mirror.
At the very beginning, when Brad pulls up beside one of Natalie's friend's, you can see a finger on the passenger seat just above her shoulder, obviously prompting her to look at Brad.
When Natalie and Zack are talking, just before leaving the summerfest, a white screen is seen at the top of the frame.
After the car accident, Zack tells Natalie that he didn't know about the baggie of coke that Brad had. In fact, there's no indication that he knew about it either before or after the crash; the baggie is discovered by the cops when the kids' souls aren't around.