At the very end, Mr. Hanson is seen walking toward the church. Because of his stroke, he's slow and unsteady. We see several close-ups of his feet, showing how he's struggling. Two of those shots are the same footage. It's obvious, because you see that he drags his foot over a small stick in the road and stumbles - and in both shots, it is *exactly* the same.
In the opening credits, the three girls are shown running down a hill that has several flowers growing on it. In reality, the flowers were fakes, and Melissa Sue Anderson (Mary) tripped over one of the fakes during one take and gave herself whiplash.