When Homer and Marge look at the plastic wedding couple in the freezer, shots from behind show the groom with a top hat, while the closeup of the couple from the front shows the groom hatless.
When Homer and Marge enter the barn, they shut the door, but in one of the next shots, you see the pigs are let out and the door is open. Then in the next shot, when the farmer gets his pitchfork/rifle, the barn door is shut and he has to kick the door open to get inside.