Continuity mistake: Sam claims it is 12am and the the bug storm is on its way, but five minutes later the sun is shining. (00:37:00)
Factual error: When Sam and Dean show up at the crime scene to investigate, they are stopped by a woman wearing digital Army ACU's. She introduces herself as Sergeant Miranda Bates, even though she has rank insignia on her cover and her chest that identifies her as a PFC (private first class). (00:14:05)
Plot hole: When Sam and Dean realise they need to destroy the hook to stop the Hook Man, they find out that it has been reforged into something else. They state it needs to be set on fire to stop him, but if it was melted down and reforged then it has already been set on fire and the Hook Man shouldn't be latched on to it in the first place.
Visible crew/equipment: When Sam and Dean are talking to Bobby about to leave after exorcising Meg, in the bottom right corner of the screen a cameraman's arm and camera can be seen. (00:17:10)
Visible crew/equipment: When Dean thanks the professor before leaving the room, you can see the second camera pan down on the left side of the screen before it cuts to that camera's view. (00:28:40)
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)
Fan Fiction - S10-E5
Plot hole: Marie says at the beginning that Chuck quit writing after Swan Song (season 5). Later she says she hates the "Metastories" which don't happen until season 9. She couldn't have known about the Metastories since those books were not published.
Suggested correction: I was mistaken about what a 'meta-story' is when I wrote this. A meta-story is when the characters refer to their own fictional state. I thought it was referring to the Metatron stories.
Celebrating the Life of Asa Fox - S12-E6
Factual error: At the beginning of the episode it shows it taking place at Emerson Manitoba in 1980. After Mary saves the boy, Asa Fox, she drives him home. Sitting in the driveway is a Maroon GMC Sonoma circa 1994 - 2004. (00:01:45 - 00:02:30)
Continuity mistake: Dean drives the Impala to the coroner's house at the same time Sam is driving Castiel and Jack back to the bunker, also in the Impala. (00:31:15 - 00:33:45)
Bloody Mary - S1-E5
Continuity mistake: When the real Jill is being Killed the blood lines from her eyes go from smeared to "clean" lines instantly. (00:14:20)
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.
Other mistake: When Dean is listening to Sam's voice mails that he left while in Gary's body, the voice in the recordings are of Sam. If Sam was in Gary's body, they would have been of Gary's voice.
Revealing mistake: As Dean digs into the dead guy's guts and discovers the claw the pale dead guy blinks.
Hell House - S1-E17
Visible crew/equipment: Right before they light the house on fire, the shot cuts the to the hell hound guys and a cameraman is running up to them on the right. Not just an arm - his whole body, including the camera.
Taxi Driver - S8-E19
Continuity mistake: When Crowley comes to the ship and finds Kevin Tran he blew out the glass on the ship to get rid of the sigils. When Sam and Dean get to the ship to check on Kevin, and they notice he's gone, all the glass isn't broken and the sigils are still there.
Bloody Mary - S1-E5
Continuity mistake: When Sam is looking at the mirrors with night vision, we see him pause and say to Dean "Look at this." The camera then cuts to an extreme closeup of the camcorder screen and the image on the screen is different to what was on there before. (00:18:15)
Continuity mistake: At the start as we see the victim on the plane, we see a blonde woman sat in the middle seat 2 rows in front of his row. When he gets up to stretch his legs, this blonde woman has now changed to a Chinese one. (00:02:45)
Audio problem: The pilot asks Amanda how she is at the start. When Amanda replies the audio doesn't match her mouth. (00:02:10)
Continuity mistake: Dean circles the newspaper article on Sophia Carlton. When he hands it to Sam the circle is different. (00:03:20)