When Zach enters the house and Mrs. Marshall takes his coat, both his coat and his uniform bear the rank of a first sergeant with 3 stripes up and 2 down. When Spring hangs his coat in the closet, it has the rank of a Master Sergeant on it, 3up/3down.
When Zach calls Mary the first time, and Mary invites him to dinner, she gives him the address and says, "Don't be late," but she never tells him what time he should arrive. However, he still manages to show up exactly on time for dinner.
(at around 47 mins) Barbara turns on an old vacuum tube radio and Silent Night immediately begins to play without the radio warming up. Then she begins to turn the tuning knob a considerable amount, but the same song continues with no station change or static.