Ask Jeeves - S10-E6
Trivia: This episode is a nod to the game Clue. Each weapon appears in a shot. Dash grabs the revolver. Dean grabs the candlestick, wrench, lead pipe and rope. Phillip was stabbed by the knife. Also there is six people invited to the party, three men and three women, referencing the guests who usually attend the Clue game party.
Answer: Angels themselves may not have genitalia, but their vessels do. Nephilim occur when an angel in a vessel reproduces.
Greg Dwyer