When Gil and Kevin are playing the arcade game "Bad Dudes", the arcade game to the left, known as "The Main Event", is powered off at the beginning of the scene and then is powered on in the last shot.
The horse seen at the beginning of Kevin's birthday party has a small sliver of white on its forehead, the horse that Gil rides off on at the end of the party has white all the way down the front of its head.
Helen is sitting in the chair, looking at the pictures, Julie comes in and they begin to argue. When Julie runs to her bedroom and Helen jumps out of the chair, the pictures fly all over the floor. In the next scene, when Julie is picking up the pictures, they are dropped in one pile on the floor.
"Cowboy" Gil starts out with only two balloons, then the camera cuts crowd reactions. When the camera cuts back to him, there at least ten balloons, inflated and tied into his balloon sculpture, which he calls lower intestines.
During the "Electric Ear Cleaner" scene the girl is asking her mum what the item is and is looking straight ahead seemingly at her, whereas her mum is stood behind her. This is apparent for the next few shots.
Another sign that the movie was shot in Florida rather than Missouri where it's meant to be set: the booth where Julie and Tod pick up the pictures is in front of a Publix, a grocery store found ONLY in Florida until 1991. The first Publix outside Florida opened in Savannah, Georgia, in 1991.
A billboard for the Orlando Sentinel (local newspaper for Orlando, Florida) is visible at the baseball stadium, but everyone around Gil and his family are wearing St. Louis Cardinals clothes, foam fingers and inflatable bats. St. Louis, Missouri, is 1000 miles away from Orlando, Florida and Gil drives home from stadium, it's unlikely they (and everyone else) travelled all the way down to Orlando with young children just for a baseball game. Ergo the scene is presumably supposed to be set in St. Louis.
During one of the baseball scenes, a ball is hit into the outfield. The player appears to have caught it, but a ball appears on the ground beside him. Yet when he reaches into his glove to throw the ball home, it is there, while the ball on the ground is still in sight.