Changes

'''Chuck:''' We came to an understanding, so spare me your contempt Castiel, the self-hating angel Angel of Thursday. You know what every other version of you did after "gripping him tight and raising him from Perdition?" They did what they were told. But not you. Not the "one off the line with a crack in his chassis." All of you. You know, I tried and I tried and I tried, but you're all just too stupid, too stubborn. Too broken. You know what? I'm over it. I'm over you.

'''Chuck:''' Oh! The Winchesters' bunkerBunker. Are they behind that door? Is this a "Parent Trap " sort of thing?

One of the objects discovered by [[Sam]] in [[the Bunker]] resembles the Holy Grail from ''Indiana Jones and the Last Crusade''. The grail was previously seen in Sergei's trailer behind Castiel in [[14.07 Unhuman Nature]] next to the moon lamp, which was also seen in previous episodes.

:"Mortal travellertraveler, beware, know that the keys of death weigh heavily. However, if you desire to enter in the dark bottomless depths, you need a gateway."

The doorway to [[Death's Library]] being made on [[the Bunker]]'s wall is similar to [https://www.youtube.com/watch?v=YpMDlq8Gq7E this scene in ''Beetlejuice''] when the Maitlands gain entry to the Netherworld.

In past seasons, [[Chuck]] has typically been shown in light colored clothing, while [[Amara]] wore a black cocktail dress throughout season Season 11. In season Season 15, Chuck begins to wear darker or muted colors (specifically His maroon sports coat), while Amara switches to wearing colors such as yellow ([[15.02 Raising Hell]]), pink ([[15.15 Gimme Shelter]] and light grey (15.17 Unity).

[[Adam and Eve|Adam]] explains that [[God]] has been playing with him and Eve as well as part of one of His stories. They initially believed that they deserved their punishment of being exiled, but that was before God moved on to [[Cain]] and Abel. As a result, Adam has spent the past 300,000 years trying to find a way to destroy God. Throughout [[Season 9]], it's revealed that Cain took on the [[Mark of Cain|Mark]] as part of his deal with [[Lucifer]] to kill Abel and send him to [[Heaven ]] to spare him becoming his pet. Cain tried to kill himself afterwards, but the Mark brought him back as the first [[Knight of Hell]]. Dean eventually killed Cain in [[10.14 The Executioner's Song]], although Adam doesn't appear to harbor a grudge towards Dean, as he seemingly appears interested solely in helping them kill God.

'''Chuck:''' We came to an understanding, so spare me your contempt Castiel, the self-hating Angel of Thursday. You know what every other version of you did after "gripping him tight and raising him from Perdition?" They did what they were told. But not you. Not the "one off the line with a crack in his chassis.":''[[Crowley]] casually called Castiel the "Angel of Thursday" in [[6.20 The Man Who Would Be King]], which is a nod to [[Eric Kripke]] saying that he came up with the name for Castiel's character by googling "Angel of Thursday". The "gripped you tight" line is Chuck is paraphrasing Castiel in [[4.01 Lazarus Rising]] about saving Dean. Chuck's line about Castiel being "the one off the line with the crack in his chassis" recalls [[Naomi]]'s line to Castiel in [[8.21 The Great Escapist]], when she said :::''"Naomi: You're the famous spanner in the works. Honestly, I think you came off the line with a crack in your chassis. You have never done what you were told. Not completely."''}}{{TriviaQuote |Text=With a rating of 0.91, "Unity" holds the record for the lowest rated episode of ''Supernatural''.