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: Season 1 episode 2, Wendigo conflicts with this episode. Originally the wendigo information is printed on the left-hand side of the journal. On the right side is loads of symbols and text. Here the "same" page featuring the wendigo can be seen when Dean and Sam are searching for the asylum information but it's different.
Continuity mistake: Near The End of the episode when Dean is being chased by the possessed truck, Sam tells him to take a left. After he's made the left, Sam tells him to go exactly 7/10ths of a mile and stop. Dean looks at his gage and it reads 70098.3. Dean looks up, then back at it: it changes to 70098.5, but the next time he looks down it says 70100.6 and when he stops it says 70101.0, meaning he's gone 2 miles too far. (Probably meaning it took two shots to get the scene right but they messed up on the gage.) (00:35:00)
The Benders - S1-E15
Continuity mistake: When the Deputy handcuffs Dean to the car door handle, he uses a small radio/cell antenna from the car to pick his handcuff lock (attached to his wrist), just as the bad guys walk toward the car. When the bad guys get to the car Dean is gone and so are the handcuffs (including the cuff that was attached to the door handle). Dean did not have time to pick both handcuff locks.
Hell House - S1-E17
Continuity mistake: Both Sam and Dean show no signs of bodily damage or harm, even though in the previous episode "Shadow," both brothers were attacked and their faces had been slashed by the shadow demons summoned by Meg.
Suggested correction: First part of the episode, it said "2 months ago" below the place where the episode takes place. So it probably took place before episode 16.
Thats before they showed up when the first group of kids went on the house and found the girl hanging.
Continuity mistake: As Sam is looking for the next victim in his visions, she walks by with her baby in a stroller. The baby is a completely different looking doll the first two times shown, but is blue-eyed Rosie when Sam approaches and interacts with her. (00:12:30)
Continuity mistake: At The End of this episode Dean suggests they go to the Grand Canyon because they have never been, later in the series they talk about John taking them when they were little.
Playthings - S2-E11
Continuity mistake: In one scene Sam is hung over the toilet from drinking too much with his cast on his left arm. The rest of the show the cast is on his right arm. (00:20:19)
All Hell Breaks Loose: Part 1 - S2-E21
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.
All Hell Breaks Loose: Part 1 - S2-E21
Continuity mistake: In the scene where Dean is with Bobby at the burned down Roadhouse and Dean gets Andy's vision about where Sam is, the first time Dean scrunches his face in pain he puts his left hand to his head. The shot changes to a back view and you can tell his left hand is still at his head. But when the shot switches again Dean is bringing his right hand down from his head.
All Hell Breaks Loose: Part 2 - S2-E22
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.
Continuity mistake: When Bella first counts her cash, the bills are all in hundreds. The camera changes angles and the bottom bill becomes a fifty.
A Very Supernatural Christmas - S3-E8
Continuity mistake: In 'A Very Supernatural Christmas' (S3E08), when the Gods are beginning to sacrifice Sam and Dean, they slice Sam's right forearm. However, at The End of the episode, Sam has his left forearm bandaged, not his right.
Continuity mistake: In the scene where Dean uses the silver knife to cut his arm to prove he is not a shape shifter, a few moments later Dean is showing Bobby the hand print on his arm, and the cut is miraculously gone. (00:13:00 - 00:15:00)
Continuity mistake: When Sam approaches Pamela to give her a hug, you see his hand on her arm. In the next shot he is still walking towards to her and his arm is hanging at his side.
Continuity mistake: In this episode, Dean says he was born in 1979. In the first two seasons, in the flashback to their mother dying, that's in 1983 which would make Dean 4 years old. He's definitely not 4 years old in the flashbacks.
Continuity mistake: When Dean is speaking to Sam, who is now Lucifer, he starts crying. Tears are physically on his face but in the next shot the tears are gone.
Continuity mistake: Gary (disguised as Sam) sits at the bar and orders a banana daiquiri. The woman next to him tries to engage him in a conversation as he sips his drink, and each time the camera switches between him and the woman, the level of his drink changes noticeably up and down.
Continuity mistake: When Sheriff Mills and Bobby are talking about transferring Rufus, her lapel goes from being under her seatbelt to over several times in subsequent shots.
Mannequin 3: The Reckoning - S6-E14
Continuity mistake: When the guys tip Rose into the grave, her eyes are open, but as she lands and dirt falls over her face, her eyes are closed. A dead person's eyes don't close on their own. (00:25:20)