When Tesla hears that Henry is going to be a father, he says that is the eighth sign of the Apocalypse. The Book of Revelations only lists seven signs of the Apocalypse.
This episode sees Helen Magnus, played by Amanda Tapping, sneak into Area 51. In Tapping's previous sci-fi series, 'Stargate SG-1', her character, Dr. Samantha Carter, briefly worked at Area 51.