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)
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.
Hibbing 911 - S10-E8
Revealing mistake: Sam types the address Donna gave him into an untitled note, which is supposed to act as a Maps search engine. A second later, a map with the address pulls up. His phone also says it's 9:56/9:58 a.m. (00:31:15)
Character mistake: Sam describes the books as being from "pre-Biblical lore" and then says they are written in Aramaic. Aramaic was a language during New Testament Biblical times and didn't exist in pre-Biblical times i.e. prior to 4000 B.C.E.
Suggested correction: I believe he meant the book "contained" pre-biblical lore.
Keep Calm and Carry On - S12-E1
Continuity mistake: Mary does not recognize adult Dean and claimed that her Dean is 4 years old. In Season 1 Episode 9: Home, she recognized adult Dean and Sam.
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)
First Blood - S12-E9
Character mistake: Sam points out Elk Mountain, but there is no Elk Mountain in Rocky Mountain National Park.
There's Something About Mary - S12-E21
Revealing mistake: At the start of the episode when Dean calls Ketch, Dean's phone is not in Call Mode.
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)
Continuity mistake: When Jack tries levitating a pencil, the pencil completely vanishes after he sets it down again.
Other mistake: In the original "Scooby-Doo" episode from which this episode is taken from, the house for the reading of the will was on an island as the Mystery, Inc. gang travelled to the house via motorboat. In this episode of "Supernatural", Sam, Dean, and the Mystery, Inc. Crew merely drive up to the house.
Continuity mistake: After Dean zaps the TV with the remote, he lowers his right arm. The next shot behind Dean's right side shows him lowering his arm again.
Back and to the Future - S15-E1
Other mistake: After the spell is cast, the ghosts are chasing Sam, Cas, the mom and the girl towards the safety line...despite ghosts being able to teleport themselves short distances, as they were doing only minutes earlier. They could easily have jumped ahead of them, instead they gave chase on foot.