During the roller-coaster scene, the cars that go into the tunnel are a different set than those that come out. The lead car is green with a cage-like device going in and red with no cage coming out.
After the roller coaster ride, Margy gets off and sees the roller coaster going up for the next run and Pat and Margy are still on it as well as the same two young couples sitting in front of them.
The ground of the camp switches from dirt to grass just after Mrs. Frake talks to her friend. The trees and lighting are also inconsistent between the actual outdoor shot and the studio set.
Women's lipstick disappears and reappears repeatedly... until they kiss someone,which they always do without lipstick.
At the beginning (and end) of the film, a large billboard poster announces the State Fair, "week commencing August 23". Midway through the film, the program of events for the jams, jellies, pickles, and mincemeat day is shown, dated Friday, August 22nd.
During a number of the outdoor scenes at the fair, mountains can be seen in the background that are far taller than any mountains that are found in Iowa.
Several of the trees seen on the Frakes' property early in the film are recognizably eucalyptus trees, with their sparse leaves and white trunks. Eucalyptus trees grow easily in California and in similar climates (e.g., around the Mediterranean or in Australia), but would not survive the harsh winters in Iowa.
During the penultimate scene (the veranda scene), as Wayne Frake steps off the veranda, the camera tracks right, and the shadow of the boom mic appears on the wall of the house as Wayne continues to move off set.