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.
Answer: Angels themselves may not have genitalia, but their vessels do. Nephilim occur when an angel in a vessel reproduces.
Greg Dwyer