Towards the end of the film, suddenly John has a completely different haircut for a few scenes, then its back to normal for the rest of the film.
After blood covers the windshield, John gets out of his car and looks at it, but it's not there. Then from the next angle it's there again.
When the alien hand first reaches out and grabs John, you can clearly see the person's wrist after the alien glove ends.
At one point John looks at his wrist before saying "It's about 3:30." Only he doesn't have a watch on.