Season 15 Callbacks
The final season of Supernatural has many returning characters, and callbacks to events of earlier seasons.
Creatures and Spirits
Spells and Weapons
- The soul catcher, a device Rowena used in 11.23 Alpha and Omega to collect souls and make the soul bomb to use against Amara is used to capture the Hell Ghosts.
- Rowena has to remove her resurrection charm that she has twice before used to cheat death.
References to past events
- Dean speculates that Chuck's actions may have unlocked the Lucifer's Cage and freed Michael where he was trapped at the end of 5.22 Swan Song.
- Belphegor refers to Dean's time in Hell as a torturer under Alastair.
- Confronted with John Wayne Gacy's ghost, Sam has to face his fear of clowns.
- We Got Work to Do - In 15.01 Back and to the Future, Sam says it and closes the trunk, while the image briefly flashes to the Winchesters closing the trunk at the end of 1.01 Pilot.
- Ketch and Rowena refer to their previous meeting, when the British Men of Letters captured Rowena several years prior and during her interrogation Ketch discovered that she implanted a special charm that could revive her if she is ever killed. In exchange for her release, Ketch made a deal with her to have the same charm implanted in his body, which he later used when he was killed by Mary Winchester.
- Francis Tumblety attempted to absorbed Kevin Tran's spirit, the last time this act among ghosts had been seen was with Whitman Van Ness in 7.19 Of Grave Importance.
- Ketch's alias "Mr. Blackmore" in 15.03 The Rupture is possibly a reference to Elizabeth Blackmore who portrayed Lady Antonia Bevell.
- Lilith is referred when her method of controlling demons working on Earth is explained via her crook, which offers a way to stop the "ghostapocalypse."
- Belphegor's plan to take in a vast number of souls so their power would make him invincible and God-like, recalls Castiel actions in opening the portal to Purgatory and absorbing the souls there. This gave him great power and he proclaimed himself God.
- Rowena's sacrifice in 15.03 The Rupture is similar to both Sam's in 5.22 Swan Song and Crowley's in 12.23 All Along the Watchtower. Her last words, "goodbye, boys," mirrors Crowley's own "bye, boys."
- In 15.04 Atomic Monsters, Sam's nightmare is of a world where he embraced the demon blood and went full Dark Side. It's revealed that he had killed Bobby and Jody and is the leader of a demon army, as Azazel intended in 2.21 All Hell Breaks Loose: Part One. When he kills Dean with his psychic powers, his eyes go black as they did when he killed Lilith in 4.22 Lucifer Rising.
- In 15.04 Atomic Monsters, Becky Rosen references the plot to 7.08 Season Seven, Time for a Wedding! in which she drugged Sam with a love potion and married him in Las Vegas.
- Chuck typing the story on Becky's computer at the end of 15.04 Atomic Monsters is reminiscent of the ending of 9.18 Meta Fiction when Metatron is typing more recent events in the form of a story on his typewriter. Both characters also talk about knowing the end of the story and working out how they get there.
- The name on the crypt that Sam, Dean, and Castiel take refuge in is "Carver," a reference to previous Supernatural writer and showrunner, Jeremy Carver.
- In 15.04 Atomic Monsters, we find Becky is still a Supernatural fan, writing fanfic and making minatures. The Supernatural merchandise in Becky's house was a combination of commercial Supernatural merchandise, items made by fans, and some made by the show. The plaid quilt and other sewn items were made by Stef aka @arachnobite who also made Jensen's Red Hood and Batman costumes. A carved Supernatural themed chess set in the living room was gifted to Jared at the EyeCon in September 2008 by by Sandra Echeverri (@Sanpao19).
- Becky's notes about Chuck's new manuscript can be seen as a meta commentary on the episode itself. Many of her notes such as there being no classic rock and neither Sam nor Dean mentioning Castiel and a cornered Sam and Dean listening to the "villain's" monologue happen in the episode. Her claims of low stakes cause Chuck to write a new dark ending, which is mirrored in the episode when he disintegrates Becky and her husband.