Audio problem: When Dean and Castiel are speaking to the police officer, Dean and Cas say "nothing" and "demons" at the same time. The second time this happens, Cas' voice says demons but his mouth is not moving. (00:11:55)
Continuity mistake: When Dean is speaking to Sam, who is now Lucifer, he starts crying. Tears are physically on his face but in the next shot the tears are gone.
Continuity mistake: Gary (disguised as Sam) sits at the bar and orders a banana daiquiri. The woman next to him tries to engage him in a conversation as he sips his drink, and each time the camera switches between him and the woman, the level of his drink changes noticeably up and down.
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.
The Song Remains the Same - S5-E13
Factual error: When Anna travels back in time, she lands on the hood of a Pontiac trans am. Castiel later comments Anna is in the year 1978, but the the Trans Am Anna falls has the front end of a 1979-1981 model.
Revealing mistake: After Sam (Lucifer) beats the crap out of Dean's face, when he's sitting on the ground, you can tell he's got something stuffed in his mouth to make his cheeks and lip look swollen.
Answer: Angels themselves may not have genitalia, but their vessels do. Nephilim occur when an angel in a vessel reproduces.
Greg Dwyer