The spell which Donatello gives Sam and Dean includes the ingredients Balthazar used to send them to the World Without Supernatural in The French Mistake (2011): "Cleanse the holy altar with sacramental water, built on a bed of godsroot. Bless the altar in the tongue of God. Coat a bronze bowl with Oil of Abramelin. Combine dragon's blood, wolfsbane, angelica root. Crush into a fine paste. Sprinkle with goofer dust [...] Mortar and pestle, combine with dead sea brine, virgin lamb's blood and the bone of a lesser saint [...] Mixture, paint three symbols [...] surrounding the altar [...] pastes into the [...] mix thoroughly, top with dried [...] Hearts of Gog and Magog."
This episode aired on Jensen Ackles' 40th birthday.
In the scene where Dean, Sam and Castiel talk about what happened with Donatello, Dean asks Cas what gives him the right to do what he did and Cas said "No one gave it to me, I took it." This mirrors directly what Lucifer said to Baldur in the season 5 episode "Hammer of the Gods".
According to Mary Winchester, Jack is supposed to be six months old, which implies that this episode is set in November 2017.
There is a deleted scene where Dean and Castiel talk in the place where they come to find Gog and Magog. It was posted on the director, P.J. Pesce's Instagram page.