The last time that Sport jumps in the pool to return to Aunt T's house, she is wearing a housecoat over her swimsuit. When she surfaces on 'the other side', she is no longer wearing the coat. Apparently the surfacing scene is the same scene used for their original arrival.
In the long shot where the parents go over to the pool to look for the children and tell them about getting divorced, the cement on the side of the pool is dry. When the children re-appear in the pool, the next long shot now shows that the cement is all wet, as if they had just jumped in the pool before the shot.
The cake in the first scene w Auntie T had chocolate icing. When the kids returned, the cake had white icing.
In the second scene with Aunt T, Jeb silently mouths Sport's lines as she recites them.
Jeb is silently mouthing Sport's line "Where'd you come from?" when the country boy pops up in their pool.
During the swimming pool scenes, Sport's voice is clearly that of an adult and not a child.
The parents appear to have Northeastern accents, whereas their children speak in Southern drawls.