Continuity mistake: The baby gets into the fridge, which then closes - we see a closeup shot of the babyproofing clip shutting itself. Then when the mother sees the spilled milk and realises what's happened, there are a few shots of the fridge - in shots from the front the clip's open, and in shots from the side it's closed. When she goes to open the fridge it's open again - she even fiddles with it to give the appearance of undoing it before opening the fridge door.
Continuity mistake: During the scene where Sam is tied up and eventually fights the fake-Dean in Becka's house, there is a shot that shows both his feet and hands tied. During the fight, both his hands and feet are shown free, but he only cut free his hands, and began fighting immediately after that.
Continuity mistake: When Dean reads about the Roosevelt Asylum in his dad's journal, there is a picture of a Wendigo on the opposite page of the newspaper clipping but in a different scene, Dean checks the article again for information on the South Wing in the Asylum but this time on the opposite page of the newspaper clipping, there is no picture.
Continuity mistake: In the scene when John is talking to Mr. D in the diner, Mr. D tells John to "say hello to your old man for me." It is later revealed in season 8 that John's father left them when he was young. This is a mistake, unless Mr. D is referring to John's grandfather (unlikely).
Continuity mistake: Before the Roadhouse fire, Ash and Dean are talking on the phone. Ash looks at his watch, on his left hand, it says 8:10, and has a black dial/face. As Dean and Bobby go through the rubble, Dean identifies Ash by his watch. Still on his left hand, it is now upside down, evident by the crown of the watch (used to move the hands of the watch) which previously facing his hand, is now facing his elbow. Also, the dial/face of the watch is now silver instead of black. This is a different watch, and was inadvertently put on the burnt arm upside down.
Continuity mistake: When Dean kisses the Crossroads Demon, his head is tilted left, but when it cuts to the next shot his head is tilted to the right. It switches back and forth in the next two shots too quickly for Dean or the demon to move their heads.
Audio problem: Dean is in the cemetery talking to his father's grave, trying to figure out what's happening to him. In a continuous shot, right after Dean says "like it doesn't want me to be happy", you hear him say, "of course I know what you'd say" but his mouth doesn't move at all.