In the scene when Tommy is talking to the police officer, officer's sunglasses go from a dull solid sliver to a glossy transparent sliver.
In the scene when they are playing baseball with Benny, Tommy is wearing different shirts between takes.
The last batter fouls off the first pitch and a runner steals second. You can't advance a base on a foul ball.
In Mr. Myrtle's house, when the bats attack the kids, you can obviously tell that the bats are fake black materials, especially when some of them get caught in the spider webs.
During the Diner scene you see the waitress give Tommy a cherry Soda. Tommy then begins to talk to Ryan when he comes in the Diner and notice he never takes even a sip of his cherry soda yet, he ask for more and when the waitress is about to fill it up it is suddenly half full again.
In the scene where Tommy and his mom are exiting the doctor's office, Tommy exclaims that he needs a drink, but if you look closely, he is mouthing something entirely different.