Revealing mistakes: When Mary (
Donna Reed) throws her rock at an upstairs window of the dilapidated old house, the rock disappears a split-second after leaving her hand, and then reappears in the distance just before crashing through the glass. The roof of the house was a matte painting, added after principal photography by the visual effects department. When Ms Reed threw her rock (and it was her throwing it, not a stand-in), the arc of its flight was a bit too high, and it crossed the matte line for most of it's travel. Consequently, it was covered up by the painting, which was added later. Appartently the live-action crew did not notice the potential problem when filming the shot.
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