Immediately after Sam repels Melanie Merchant's initial attack, he turns to Sarah Blake, whose hair is strewn across her face in a close-up. This instantly cuts to a long shot and we see that Sarah's hair is no longer covering any part of her face.
When Sam is first seen, he is in a bar, reading newspaper articles and drinking something from an old-fashioned glass, presumably whiskey. Dean brings two beers to the table. The camera pans out and suddenly the whiskey glass is gone and there are 4 full beers at the table.
When Sarah walks up to Evelyn and is about to touch her, Sam calls out, "Sarah, don't!" but Jared's mouth does not move.
When Dean opens up the wooden casket, Isaiah's skeleton is not wearing any clothes. While it may appear that this is so because the reveal of the corpse is very brief, freeze-frame at 32:56, not only reveals that Isiah has a tattered suit-coat but also the remnants of hair.
When Dean gets the woman's number at the bar at the beginning of the episode, he repeats the number back incorrectly. She gives a number ending in 3420 but Dean says it back as 7420 and the woman confirms he heard it correctly.
When Sam, Dean, and Sarah Blake examine the cursed painting after the second murder, Dean notices the razor has moved and says "Jared, check it out" - using actor Jared Padalecki's real name instead of his character's name. It is difficult to completely ascertain if Jensen is, indeed, saying "Jared" instead of Sam because Jensen is mumbling a bit. However, the box set of Season 1 and Netflix both have the subtitles set to "Sam, check it out."