Before Dean asks Emily to fill up his car, neither of them have had a chance to touch the license plate, but when she bends down to put in the fuel, the license plate is already flipped down and all she has to do is unscrew the fuel cap.
The trees in the orchard aren't apple trees, but rather appear to be hazelnuts trees.
Dean claims that he can fix a leaky brake line in an hour. A leaking brake line cannot be patched, the entire line must be replaced. This would definitely take more than an hour. Even "sundown" is pushing it a bit, given that they're in a small town with no dealerships or auto parts chain stores around.
Despite the fact that the story is set in April, the trees are not in leaf and in fact, it is clearly an autumn orchard--dead leaves, picking baskets, etc.
When Dean is checking out the scarecrow in the orchard, you can see it breathing.
After Dean shakes the Professor's hand and walks towards the door, to the left of the screen a camera is briefly visible for a couple seconds.
In the beginning during the teaser, Vince and Holly are walking through the orchard when they actually hear something behind them (the scarecrow). Right as they whip around you can clearly see car headlights and taillights to the right of their shoulders.
When the couple is startled by the noise of the Scarecrow pursuing them the camera swings around and catches either its own reflection or another camera in the shot.
When Sam and Dean are arguing in the car, Sam states that it's been six months since Jess died. If it had been six months, it wouldn't be the second week of April, it would be close to Sam's birthday, the first week of May.