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)
Visible crew/equipment: At the start of the episode, the couple comes out of the car and when it pans to show the orchard, a shadow can be seen walking in the lights.
Answer: Angels themselves may not have genitalia, but their vessels do. Nephilim occur when an angel in a vessel reproduces.
Greg Dwyer