Season 15 Callbacks

Chuck recounts his history with Sam and Dean.

The final season of Supernatural has many returning characters, and callbacks to events of earlier seasons.

Returning Characters

• Adam Milligan
• Alex Jones
• Amara / The Darkness
• Anael / Sister Jo
• Arthur Ketch
• Becky Rosen
• Benny Lafitte
• Bess Fitzgerald
• Billie / Death
• Bobby Singer
• Bobby Singer (Apocalypse World)
• Charlie Bradbury (Apocalypse World)
• Chuck Shurley / God
• Cosmic Entity (as Meg)
• Cuthbert Sinclair / Magnus
• Dark Kaia
• Donatello Redfield
• Donna Hanscum
• Eileen Leahy
• Garth
• Jenny
• Jody Mills
• Jules
• Kaia Nieves
• Kevin Tran
• Lucifer
• Michael
• Rowena
• Ruby
• Sergei
• Stevie

Creatures and Spirits

• Angels
• Archangels
• Baba Yaga
• Canids
• Clowns
• Constance Welch / Woman in White
• Cosmic Entity
• Demon Dean / Deanmon
• Demons
• Djinn
• Evil!Sam
• Grigori
• Hell Ghosts
• Hellhounds
• John Wayne Gacy
• Lamia
• Leviathans
• Lilith
• Marid
• Mary Worthington / Bloody Mary
• Nephilim
• Pagan Gods
• Reapers
• Samifer
• Shapeshifters
• Thule Society
• Vampires
• Werewolves
• Witches
• Wood Nymph
• Wraiths

Spells and Weapons and More

• 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 used the Book of the Damned to aid in keeping the Hell ghosts imprisoned and absorbing them all inside her body before sacrificing her life to imprison them all back to Hell.
• Rowena has to remove her resurrection charm that she has used twice before to cheat death.
• Becky Rosen is revealed to still be a fan of The Supernatural Books / Winchester Gospels, writing fanfic stories online and selling Supernatural merchandise on Etsy, which proves lucrative.
• In Sam's nightmare, Dean uses angel-killing bullets to kill a few demons invading the Men of Letters Bunker.
• In 15.05 Proverbs 17:3, Dean and Sam pose as U.S. Wildlife Service "Agents Ford and Hamil" using the same fake IDs from 1.03 Dead in the Water. There is a running gag that Dean doesn't look like his picture anymore, while no one comments about Sam's more visibly obvious younger photo.
• In Sam's nightmare, Dean uses the Colt to shoot Lucifer in the head, but it doesn't work and he incinerates Dean.
• Sam produces Ruby's knife to kill Lilith. Lilith remarks that he was only able to kill her in 4.22 Lucifer Rising because she let him.
• Sam's vision shows him getting killed by Dean, who was a Knight of Hell, with the First Blade used in conjunction with the Mark of Cain.
• Sam uses a devil's trap bullet to trap Lilith, although it is unable to hold her for long.
• Dean uses a witch-killing bullet to to kill Emily the witch.
• Sam and Eileen find Rowena's Spellbooks which document everything she knows about magic. These journals have only made brief cameos in previous seasons before 15.06 Golden Time. Sam completes and uses an unfinished resurrection spell Rowena originally planned to use for Mary to revive Eileen, but it's later revealed that Chuck planted half the spell in the journal knowing that Sam would complete it to revive Eileen and spark romance.
• The voodoo doll created by Emily and her mother to torture Sam appears similar to the Twigs & Twine Doll created by Miss Beverly in 12.20 Twigs & Twine & Tasha Banes.
• Dean looks to the demon tablet to find a way to trap Chuck.
• Dean grabs his grenade launcher before entering the monster fight club, but once again doesn't get to use it.
• Castiel discovers an angel sword in a victim's possessions and realizes that he was a Grigori from what Tamiel told Sam about the swords and his kind. Kabaiel tries to kill Castiel with his own angel sword, but is instead killed by Castiel with his angel blade.
• Billie uses Death's Scythe to kill Merle for failing to keep Jack in line. In addition, Merle disintegrates in the same manner that Death did when Dean killed him with the scythe.
• Sam wields Mjölnir and Dean unleashes his grenade launcher in 15.14 Last Holiday.
• Adam gives Jack one of his ribs, a Hand of God, which is the last step in his 300,000 year plan to kill Chuck. When Jack absorbs its energy, it starts an elemental chain reaction, fusing his human soul and Nephilim grace into a metaphysical supernova.
• Dean uses Death's Scythe to drive Billie away, forcing her to leave Jack, her scythe, and Chuck's Death Book after he cuts her shoulder. She reveals that the scythe kills anything it slices no matter how minor, revealing that Dean caused her death just as he killed Death five years prior in 10.23 Brother's Keeper.
• Castiel draws an angel banishing sigil on the door to the Bunker's dungeon, which acts as a protective sigil against Billie.
• Michael uses one of the archangel blades to kill Lucifer.
• Dean takes out the shurikens, which have been seen in the Impala's weapons stash throughout the whole series and have never been used.

References to Past Events

15.01 Back and to the Future

• The Hell Ghosts escaping from Hell through the fissure Chuck opened mirrors Lucifer's liberation form the Cage in 5.01 Sympathy for the Devil after Sam killed Lilith in 4.22 Lucifer Rising and inadvertently broke the last of the 66 Seals. In both cases, Sam and Dean were at the site where the gates opened before they escaped. Later, it's also revealed that the Cage was opened along with every door in Hell, allowing Michael to escape after being imprisoned for a decade since their confrontation at Stull Cemetery in 5.22 Swan Song.
• Belphegor chuckles at the idea that God opened the fissure, but his doubts go away when he sees Castiel and the Winchesters are serious. This has been seen in many previous episodes, including 1.19 Provenance, 7.20 The Girl with the Dungeons and Dragons Tattoo, 8.12 As Time Goes By, and 12.12 Stuck in the Middle (With You).
• Dean calls Belphegor "Crowley Jr.". Both Belphegor and Crowley are demons who helped Castiel and the Winchesters stop the Apocalypse. Belphegor volunteers to help returning the millions of damned souls back to Hell and Crowley offers to help retrieve the Horsemen Rings and use them to send Lucifer back to the Cage.
• Belphegor refers to Dean's time in Hell as a torturer under Alastair between Seasons 3 and 4.
• Confronted with John Wayne Gacy's ghost, Sam has to face his fear of clowns like in 7.14 Plucky Pennywhistle's Magical Menagerie.
• When Castiel heals Sam's cut, he also mends the tear in his clothes. He has previously displayed this ability in 8.07 A Little Slice of Kevin.
• One of the ghosts released from Hell resembles Lizzie Borden, a murderer from Fall River, Massachusetts, referenced in 11.05 Thin Lizzie who killed her father and stepmother in her house with a hatchet. Fall River, Massachusetts, is also where Crowley, Lucifer, and Asmodeus based their Earth-side operations in the Needham Asylum between Seasons 10 and 13.
• Belphegor's spell to make a mile-wide force field to prevent any ghosts from entering and exiting Harlan, Kansas, is reminiscent of Samuel Colt's 100 square mile devil's trap surrounding the Devil's Gate in Wyoming in Fossil Butte Cemetery from 2.22 All Hell Breaks Loose: Part Two.
• Sam says "We Got Work to Do" and closes the trunk, while the image briefly flashes to the Winchesters closing the trunk at the end of 1.01 Pilot.

15.02 Raising Hell

• Francis Tumblety (Jack the Ripper) is one of the few ghosts of famous serial killers the Winchesters faced. They previously faced Dr. H.H. Holmes (Herman Webster Mudgett) in 2.06 No Exit and John Wayne Gacy (Pogo the Clown) in 14.13 Lebanon. Ironically, both Tumblety and Holmes were doctors in life and were both trapped by the Winchesters by the end.
• 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 in 12.22 Who We Are.
• Belphegor stated that souls from Hell can't go to Heaven, though John and Bobby went to Heaven in 2.22 All Hell Breaks Loose: Part Two and 8.19 Taxi Driver following their time in Hell, but he explains that Chuck made an exception for them. In 5.16 Dark Side of the Moon, Joshua tells Sam and Dean that God had granted them salvation into Heaven, implying that they were only allowed in because of Chuck. However, Bobby's entry into Heaven was a part of the second trial to close the Gates of Hell, and the trials were recorded in the Demon Tablet by Metatron at a time when Chuck still cared about humanity.
• Francis Tumblety attempted to absorb 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.
• Rowena created another soul catcher much like the one used in 11.23 Alpha and Omega, though unlike last time, it can only capture a few ghosts at a time and the magic word is "Capare" instead of "Haggis." Despite how different both soul catchers are, they are both powerful weapons regardless of how many souls they contain.
• When Dean apologizes for shooting Ketch with iron bullets, Ketch admits Dean's been itching to kill him again after Mary killed him following their fight in the Bunker in 12.22 Who We Are.
• Amara talks about how Chuck and his archangels sealed her away, as mentioned by Death in 10.23 Brother's Keeper, and is now doing the same thing to him in his weakened state.

15.03 The Rupture

• Lilith is mentioned when her method of controlling demons working on Earth is explained via her crook, which offers a way to stop the "Ghostpocalypse."
• Ardat finds out their plans by posing as Arthur Ketch on his cell phone after killing him. Ketch previously posed as Mick Davies in the same manner after killing Mick in order to trick the Winchesters into a hunt so that he and a team could bug the Bunker in 12.18 The Memory Remains.
• Belphegor says that Lilith was the only demon in Hell who could read Enochian, but Crowley and Abaddon have been known to read and write Enochian fluently.
• 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 Purgatory and absorbing the souls there. This gave him great power and he proclaimed himself the new God until he returned the souls to Purgatory.
• Belphegor had plans to become the new King of Hell after averting Chuck's "Ghostpocalypse," much like how Crowley became the King of Hell for six years after helping Castiel and the Winchesters stop the Apocalypse by sending Lucifer back to the Cage along with Michael, Adam Milligan, and Sam. Unlike Crowley, Belphegor is more interested in taking control of everything else by taking Chuck's vacant spot as the new God.
• Castiel barely musters enough strength to kill Belphegor along with the souls he absorbed, destroy Lilith's Crook, and incinerating Jack's body. This is similar to when he barely gathered enough strength to split the demon tablet in half and banish Crowley in his weakened state after Naomi sent an incursion of her angels to rescue him from Purgatory in 8.07 A Little Slice of Kevin.
• Jessica tells the Winchesters that Rowena gets killed by Sam in every version of her permanent death in 13.19 Funeralia. With Rowena's assistance, Sam driving the knife into her belly, fulfilling her destiny.
• Rowena's sacrifice is amalgamation of Sam's sacrifice in 5.22 Swan Song and Crowley's sacrifice in 12.23 All Along the Watchtower. Her last words, "goodbye, boys," mirrors Crowley's own "bye, boys." She falls into Hell along with all the Hell Ghosts, much like how Sam imprisoned Lucifer along with Adam and Michael.
• Castiel says his powers have been fading after Chuck declared "The End." All throughout Season 5, Castiel slowly started losing his powers until they were completely drained in 5.21 Two Minutes to Midnight. He regained his powers with some upgrades at 5.22 Swan Song after God revived him as a Seraph.
• Dean's distant demeanor towards Castiel following the deaths of Jack and Mary and the revelation of Chuck's deception mirrors his loss of faith in Sam between Seasons 4 & 5 after he chose Ruby over him, gave in to his addiction to demon blood, killed Lilith with his psychic abilities, and started the Apocalypse by freeing Lucifer from the Cage.

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 went black as they did when he killed Lilith in 4.22 Lucifer Rising.
• In the Bunker's kitchen, Benny's last words to Dean are "I'll see you on the other side, brother," mirroring what Benny said to Dean in 8.07 A Little Slice of Kevin before getting carried out of Purgatory. Benny also calls Dean "brother" all throughout Season 8.
• Dean shows a vampire fang to Sam to confirm the type of monster they're dealing with, similar to when John found a vampire fang at a crime scene in 1.20 Dead Man's Blood and shows it to his sons to confirm that a couple was captured by the local nest led by Luther and Kate (Vampire).
• 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.
• Becky encouraging Chuck to write is a mirror image of when Zachariah visits him 4.18 The Monster at the End of This Book. Unlike Becky, who encourages Chuck to write to get him out of his blues, Zachariah forces him to stay alive and write to continue and finish writing the Winchester Gospels, threatening to stop him if he attempts disclosing Sam and Dean's future to the Winchesters.
• 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.
• Sam admits that he still thinks about Jessica since her death at the hands of Brady in 1.01 Pilot and can't stop thinking about what happened to her, despite having gotten his revenge on him near the end of 5.20 The Devil You Know or Dean killing Azazel in 2.22 All Hell Breaks Loose: Part Two after ordering his demon gang to kill Jessica and persuade Sam to return to the hunting life and learn to hone his growing psychic abilities.

15.05 Proverbs 17:3

• In Sam's nightmare, Dean attempts to kill the Lucifer-possessed Sam with the Colt, only to have Lucifer heal the injury and burn Dean alive. This references both when Dean tried to kill Lucifer, possessing Nick, in 5.10 Abandon All Hope... and similarly failed, and when his alternate 2014 self tried to kill the alternate 2014 Lucifer with the Colt while he was possessing Sam in 5.04 The End. The nightmare Lucifer even wears the same white suit from the latter instance.
• The beginning scene where Ashley Monroe and her friends are stalked by the werewolves Josh and Andy May, is reminiscent of the scene from 1.02 Wendigo where Tommy Collins and his friends are stalked by the wendigo. In both episodes, three people are attacked at their campsite located in the Colorado wilderness and two of them are taken before the monster moves on to the third, who in both cases survives the attack.
• In 15.03 The Rupture, the demon Malfayan rationalized his looting of Lilith's Chamber by telling Belphegor and Castiel, "What? Not like Lilith's coming back." Lilith of course would make her return in "Proverbs 17:3".
• One of Lilith's lines as Ashley Monroe was, "Wouldn't it be great if everything was just planned out for you? If it was all just already decided?" to which Dean replies it wouldn't be. Gary Frankel, disguised as Sam, asked Dean "I don't know. You ever feel like your whole future is being decided for you?" in 5.12 Swap Meat, and Dean says it feels like that happens a lot, to which Gary replies, "No matter how much you fight it, you can't stop the plan. The stupid, stupid plan."

15.06 Golden Time

• Castiel uses the alias "Clarence Worley" while working a djinn case in Wyoming. Clarence was Meg's nickname for him through Seasons 5 and 8.
• The Bunker is shown to have a phone setup similar to Bobby Singer's and Garth's, used to back up aliases for hunters in the field. Like Bobby and Garth, Dean backs up Castiel's FBI alias. However, Dean simply hangs up on Castiel, leaving him to pretend he's still talking on the phone in front of the sheriff.
• Dean uses Bobby's old FBI alias "Assistant Director Kaiser" that he had used in 4.14 Sex and Violence.
• Sam tells Emily that Dean once put superglue in his toothpaste when he was 10. In multiple seasons, Sam and Dean occasionally start pranking each other, which ends up escalating to the point where it causes bodily harm, notably in 1.17 Hell House. Ironically, Sam also rubbed superglue around Dean's beer bottle, which made him peel the skin off his palm to remove it.
• Sam made a hex bag and used it to kill Jacinda's mother by shoving it in her mouth. He originally learned how to make hex bags from Ruby between Seasons 3 and 4, designed to hide their location from angels and demons. By this point, Sam also learned a few tricks from Rowena, having learned how to cast killing spells using hex bags he designed.

15.07 Last Call

• While Dean catches up with Lee Webb, he mentions how he suffered from ghost sickness at the hands of the buruburu Luther Garland in 4.06 Yellow Fever.
• Dean and Lee Webb were hunting buddies while Sam was in Palo Alto attending college at Stanford.
• Lee tells Dean he can't just sit around lip-syncing "Eye of the Tiger" when no one is watching, a reference to the outtake of Jensen lip-syncing at the end of 4.06 Yellow Fever.
• Dean sings karaoke with Lee Webb, which is a reference to singing karaoke in 10.01 Black during his demonic misadventures with Crowley. Dean even wears the same clothes on both occasions. Dean also comments on how the last time he sang karaoke, he got food thrown at him.

15.08 Our Father, Who Aren't in Heaven

• Donatello and the Winchesters worry about him going insane again when he reads the demon tablet as he did in 13.14 Good Intentions.
• God speaking through Donatello is similar to Lucifer speaking to Nick through him from the Empty in 14.17 Game Night following an injection of angel grace.
• There are a number of references to the (first) Apocalypse, and Adam / Michael being locked Lucifer's Cage with Sam / Lucifer.
• When greeting the Winchesters and Castiel as the new Queen of Hell, Rowena goes "hello, boys," her son Crowley's traditional greeting to them.
• Rowena's admonishing of Dean and Castiel to fix their friendship is similar to Ellen Harvelle's spirit threatening to kick Dean's ass from beyond the grave if he didn't talk to Sam in 7.07 The Mentalists.
• God, disguised as Sue Barrish, communicates with Eileen Leahy in a similar manner to how He communicated with Becky Rosen in 5.01 Sympathy for the Devil while disguised as Chuck Shurley and passing on the message about the Michael Sword.
• Michael killing Lilith in a flash of white light is a reference to Lilith's love for attacking her enemies with blasts of white light, as seen in 3.12 Jus in Bello and 3.16 No Rest for the Wicked. In the former case, she was believed to have killed Nancy Fitzgerald and Victor Henriksen in this manner until Henriksen revealed otherwise during the Rise of the Witnesses in 4.02 Are You There, God? It's Me, Dean Winchester.
• Michael acting like a petulant child mirrors Lucifer's own childish tantrum in 11.22 We Happy Few after being reunited with God. In Michael's case, he retreated behind Adam so that he didn't have to listen anymore. In Lucifer's case, he hid out in Sam's room to avoid God.

15.09 The Trap

• Dean and Castiel make several references to their time in Purgatory between Seasons 7 and 8.
• A Leviathan reveals that Benny was ripped apart by vampires for helping Sam and Bobby escape after the events of 8.19 Taxi Driver. Benny is still a Purgatory legend for escaping from Purgatory and then returning.
• The Leviathan tells Dean and Castiel that Eve wants revenge for killing the Alphas and absorbing all of the souls of Purgatory.
• Chuck's threats to persuade Sam not to imprison him are reminiscent of Zachariah's attempts to convince Dean to give Michael his consent in 5.04 The End. Both parties show the Winchesters alternate futures where they live in an apocalyptic version of Earth and eventually lose in the end. Both versions of Dean in these alternate futures lose hope in themselves and their allies. However, while Dean continued to refuse to give his consent, Sam is more receptive to the alternate future he sees.

15.10 The Heroes' Journey

• Garth once again displays his tendency towards hugging people. This time, Dean proves to be more receptive.
• Sam and Dean meet Garth's daughter, Gertie Fitzgerald. Garth previously mentioned having a daughter with Bess Myers in 14.09 The Spear. He is also revealed to have recently had two twin boys which he named after Sam and Castiel.
• Dean and Garth remark on Garth's claims to have killed the Tooth Fairy on his very first case. Garth insists that, "She had it coming."
• Dean tells Cutty that the Winchesters have killed demons, angels, Alphas, and gods.
• The fight club promo for the Winchesters' fight uses their mug shots from 2.19 Folsom Prison Blues.
• Garth is once again knocked out by a monster during a fight. However, this time he recovers in time to kill the monster and save the day. Garth once again quips that an enemy, "Got Garth'd" after disposing of them as he did in 7.18 Party On, Garth.

15.11 The Gamblers

• After Sam comments that he'd originally thought the coins from Fortuna's Alaskan pool hall were hexed or cursed, Dean brings up the Rabbit's Foot from 3.03 Bad Day at Black Rock which was cursed to give the owner good luck which turned sour after the object was lost.
• The Winchesters refer to their past of hustling pool to make money to survive, something that hasn't been seen since 10.17 Inside Man. It's also shown that, unlike many of their other skills such as lock-picking, Sam and Dean really are good at pool on their own from their years of experience without the added luck God gave to them.
• Fortuna's pool hall is similar to the witch Patrick's poker games in 5.07 The Curious Case of Dean Winchester. In both cases, the victims die if they lose too much, and both Fortuna and Patrick choose to play against Sam rather than take on Dean for a rematch. However, unlike Fortuna who skims luck off of each person's winnings, Patrick detests cheating, relying on intuition rather than reading minds or using magic to rig the game in his favor. Sam, who is not as skilled as Dean at pool or poker, manages to beat them both.

15.12 Galaxy Brain

• At the end of 15.09 The Trap, Dean refers to Chuck's plan as "galaxy-brained", and tells Him to, "Go back to Earth 2 and play with your other toys." This episode begins "Four Weeks Ago" on Earth 2, and one of the TV screens Chuck turns on in the Radio Shed shows the ending conversation with Sam, Dean, and Castiel from "The Trap". Chuck then proceeds to "play" with his other "toys" for the next few weeks by destroying every alternate universe. Sam previously called Apocalypse World "Earth 2" in 13.13 Devil's Bargain and Dean called the French Mistake World "Earth #2" in 6.15 The French Mistake.
• Jack looks at Mary's initials on the library table.
• Dean and Castiel talk about how he and Kelly Kline recognized Jack's goodness in previous episodes.
• Sam mentions the Cosmic Balance to Castiel after learning Jack is to kill God.
• Dean mentions having seen Death's Library from 13.05 Advanced Thanatology.
• Sam reminds Dean and Castiel about Ma'lak Box and how it was a plan of Billie's that failed.
• When Dark Kaia demands her spear back, Dean says it was destroyed. Michael snapped it in two in 14.09 The Spear. The remnants of the spear were left behind in the penthouse apartment of the hotel in Kansas City, Missouri.
• Dark Kaia reveals that when she accidentally stabbed Kaia Nieves with her spear in 13.10 Wayward Sisters, she tended to her wound before making her way to the Winchesters' world, revealing that Kaia is alive in the Bad Place and has been fending for herself for two years.
• Jody explains that after Kaia's supposed death, Claire became obsessed with seeking revenge for two years, particularly after Jody told her that Dark Kaia had made her way to their world.
• Jack uses his powers to dreamwalk with Dark Kaia, which mirrors the time he dreamwalked with Sam, Dean, and Kaia in 13.09 The Bad Place.
• Merle talks about when Amara penetrated the warding in the Bunker to enter it in 11.22 We Happy Few.
• Castiel talks to Jody about how he took everything from Claire when she was younger and he may never forgive himself for it.
• Merle's death mirrors Death's death in 10.23 Brother's Keeper.
• Dean remembers his first meeting with Death in Chicago during the Apocalypse a decade ago in 5.21 Two Minutes to Midnight, where Death prophesied that he would one day reap God in the end.
• Billie explaining Chuck having to make Himself apart of the framework of existence, is similar to Chuck telling Sam and Dean that's written himself into the story in 4.18 The Monster at the End of This Book.

15.13 Destiny's Child

• The alternate Sam and Dean arrive when their car appears in the middle of the Bunker's armory, mirroring how God teleported the Impala into the same location in 11.21 All in the Family.
• Dean talks about Sam's theory of the Cosmic Balance from 11.23 Alpha and Omega, hypothesizing that if Chuck and Amara are both killed, the universe would continue to operate.
• When Sam and Dean visit Sister Jo, they briefly remind her of Castiel's prayer to God through Joshua's Amulet in 14.17 Game Night.
• While talking in the first flashback, Jo and Ruby mention Ruby's first blonde meatsuit from Season 3.
• Sister Jo's betrayal of the Winchesters in 15.13 Destiny's Child mirrors Anna Milton's betrayal in 5.13 The Song Remains the Same.
• Several references are made to Sam and Ruby's prior relationship and her death at the hands of the Winchesters.
• Castiel and Jack talk about Mary's death from 14.17 Game Night and 14.18 Absence. While Jack acknowledges that what he did was a mistake, he still doesn't feel anything because of his soullessness, which disturbs him.
• The Cosmic Entity takes on the form of Meg and uses her term of affection "Clarence" for Castiel, even greeting him with Meg's customary "Hello, Clarence."
• The Meg Cosmic Entity refers to Castiel as "pizza man," a reference to 6.10 Caged Heat, where Castiel kissed Meg and told her he "learned it from the pizza man," as well as 8.17 Goodbye Stranger, where Castiel tells Meg he remembered the pizza man and that it was a good memory.
• In the real memory of Ruby's meeting with Jo concerning the Occultum, Ruby says if her call was a trap, she would "mess [her] up." Throughout Season 4, Ruby was shown to be afraid of angels and always keeps herself at arm's length from their affairs.
• Jack, Castiel, and the Cosmic Entity mention Castiel's deal with the Entity in 14.08 Byzantium.
• Jack visits the Garden of Eden, which was referenced in multiple previous seasons. Gadreel from Season 9 was the angel tasked to guard the Garden of Eden and prevent evil from entering. However, he somehow allowed Lucifer to enter the Garden which led to the corruption of humanity.
• In the Garden, Jack experiences flashes of events from several previous episodes in Seasons 13 and 14 as his soul is restored. These include:
  • Blasting Sam and Dean after being born in 13.01 Lost and Found.
  • Collapsing at the end of 14.06 Optimism.
  • Spending time with Dean and driving the Impala in 14.07 Unhuman Nature.
  • Celebrating his resurrection and discovering Michael's location in 14.08 Byzantium.
  • Talking to Kelly Kline in Heaven in 14.08 Byzantium.
  • Almost killing Stacy in 14.16 Don't Go in the Woods.
  • Killing Felix the snake in 14.15 Peace of Mind.
  • Jackifer telling him that there's no going back from killing Mary in 14.18 Absence.
  • Breaking out of the Ma'lak Box in 14.19 Jack in the Box.
  • Looking in the mirror after beating up Nick in 14.17 Game Night.
  • Exorcising Michael from Rowena in 14.14 Ouroboros.
  • Killing Nick in 14.17 Game Night.
  • Accidentally killing Mary Winchester in 14.17 Game Night and the aftermath of her failed resurrection in 14.18 Absence.
  • Dean aiming the Equalizer at Jack in 14.20 Moriah.
  • Jackifer telling him that the Winchesters will never trust him again in 14.18 Absence.
• After he gets his soul back, Jack is shown to be grieving Mary's death from 14.18 Absence and pleads with Sam and Dean to forgive him.

15.14 Last Holiday

• Dean makes reference to having killed Hitler, which he did in 12.05 The One You've Been Waiting For.
• Dean tells Sam the sleeping robe gifted to him by Mrs. Butters feels like he's wrapped in hugs, which he also told Sam when he wore a sleeping robe in 13.16 Scoobynatural.
• The flat screen TV Dean got for the Dean Cave that was broken at the end 13.16 Scoobynatural was repaired by Mrs. Butters. He initially got the TV as a reward for saving the owner of a pawn shop from a dinosaur mascot outfit possessed by a ghost.
• Mrs. Butters pulls out Sam's fingernails in a futile attempt to convince him to kill Jack. He previously had his fingernail ripped out in 3.08 A Very Supernatural Christmas when he and Dean were captured by Madge and Edward Carrigan, who were preparing a ritual to sacrifice them to Hold Nickar, Teutonic God of the Winter Solstice. Ironically, Madge, Edward, and Mrs. Butters are not fans of blue language.

15.15 Gimme Shelter

• When Jack addresses himself as FBI, he holds his badge upside-down much like Castiel did in previous seasons and Charlie on one occasion in 8.20 Pac-Man Fever.
• The picture of himself that Castiel uses to summon the crossroads demon Zack was an image of him from 13.06 Tombstone.
• Amara meeting with Sam and Dean at Pavel's Deli in Pennsylvania to discuss her joining the team to fight against Chuck is reminiscent of when Castiel met with Metatron in 8.22 Clip Show at Eugenie's Bistro in Ojai, California, to discuss their plan to undergo the trials to supposedly seal the gates of Heaven.
• Amara explains that she revived Mary in 11.23 Alpha and Omega hoping that Dean would understand that, despite how complicated she was, the real Mary was better than the one he always carried in his mind since she was real. She'd hoped her generous act would teach him that the present is always better than the past, as well as wishing it would extinguish Dean's lifelong rage over his complicated past resulting from his mother's initial death at the hands of Azazel in 1.01 Pilot.
• Castiel reattaches Valerie's severed fingers as he did for Kevin Tran off-screen in 8.07 A Little Slice of Kevin.
• The crossroads demon Zack's personality is more obnoxious than evil, much like Grab from 13.08 The Scorpion and the Frog.

15.16 Drag Me Away (From You)

• In 1993, Dean makes a reference to Sam's imaginary friend, Sully, from 11.08 Just My Imagination.
• The image of the shtriga from 1.18 Something Wicked and among John's research in 1.21 Salvation could be seen as Sam looks through the lore.
• Dean sees a hallucination of his younger self in the hotel hallway. Sam previously saw a hallucination of his younger self while detoxing from demon blood in Bobby's Panic Room in 4.21 When the Levee Breaks.
• When Dean is put in a hallucination of Baba Yaga's nest, he sees a young version of Sam dead. He had a similar vision of an adult Sam dead in the Soul Eater nest in 11.16 Safe House.
• When Dean reveals Jack's plan to kill Chuck and Amara at the cost of his life, Sam berates Dean for keeping it from him, saying he thought they were past keeping secrets from each other. Sam and Dean (and other major characters) have hidden major secrets from each other throughout the progression of the series:
  • In Season 4, Sam hid the truth about feeding on demon blood as he was trying to get strong enough to kill Lilith.
  • In Season 6, Castiel hid his alliance with Crowley from Bobby and the Winchesters while they planned to steal the souls of Purgatory, so Castiel could kill Raphael to keep him from restarting the Apocalypse and so Crowley could secure his blossoming position as the new King of Hell.
  • In Season 7, Dean killed the kitsune Amy Pond and kept it from Sam, even after knowing she saved his life.
  • In Season 8, Dean tricked Sam into going to Kermit, Texas, to supposedly save Amelia Richardson, to keep him and Martin Creaser out of the way while he and Benny hunted the rogue vampire Desmond.
  • In Season 9, Dean tricked Sam into giving his consent to Gadreel to possess him to save his life after failing to complete the trials.
  • In Season 10, Sam pretended to burn the Book of the Damned and worked with Rowena, Castiel, Charlie, and Crowley to translate it and remove the Mark of Cain from Dean's arm.
  • In Season 11, Castiel allowed Lucifer to possess him to escape from the Cage to aid in the fight against Amara.
  • In Season 12, after Sam uses the Hyperbolic Pulse Generator to exorcise Lucifer out of President Jefferson Rooney and supposedly send him back to the Cage, Crowley secretly altered Rowena's spell to send him to the Needham Asylum instead, where he had prepared his original vessel Nick to contain Lucifer's essence. He used runes and spellwork from the Cage carved into every molecule to effectively torture the fallen archangel, planning to use him as "[his] own personal nuke" to prevent any other demon from usurping the throne.
• The Baba Yaga is the fourth monster defeated years before that the Winchesters have had to come back to finish for good. The first was the shtriga in 1.18 Something Wicked, the second was the demon in 7.15 Repo Man (though it's revealed that the killer is Jeffrey who lured the Winchesters back to Coeur d'Alene, Idaho, to use Dean's blood to successfully summon the demon back), and the third was the Soul Eater in 11.16 Safe House (though the Soul Eater was an old case of Bobby's and Rufus's and not the Winchesters, and at the end of the episode, they head off to kill another one from an earlier case Bobby worked in Tennessee).

15.17 Unity

• Amara references her first meeting with Dean in 11.01 Out of the Darkness, Into the Fire, when she tells Dean they will always help each other.
• Adam corrects Dean that the forbidden fruit was a quince and not an apple, similar to when Crowley corrected Castiel in 10.23 Brother's Keeper.
• Adam said that Chuck used his sons, Cain and Abel, as part of one of his first stories, which was explained in Season 9. When Lucifer planned to make Abel into his pet, Cain offered a deal where Abel would go to Heaven and he would go to Hell. Lucifer accepted as long as Cain killed Abel, giving him the Mark. Once Cain killed Abel, he committed suicide with the First Blade to keep himself from becoming the killer the Mark wanted him to be, but the Mark corrupted Cain's soul and revived him as the first Knight of Hell.

15.18 Despair

• Jack tells Sam he has only driven once before, a reference to Dean teaching him how to drive the Impala in 14.07 Unhuman Nature.
• When Jack moves his hand towards a plant, it shrivels up and dies much like the flowers Amara touched in 11.23 Alpha and Omega.
• Billie failed to heed her own advice from 13.05 Advanced Thanatology, when she left her scythe lying around in the vicinity of Dean, leading to her own demise.
• Billie reveals that Death's Scythe slowly kills anything it cuts, even if it's not a killing blow, causing the bodies to slowly rot. This is reminiscent of the Lance of Michael from 12.12 Stuck in the Middle (With You) which causes angels to die slow and painful deaths as their bodies deteriorate.
• Billie references Castiel stabbing her in the back and killing her from 12.09 First Blood.
• Billie attempts to kill Dean by crushing his heart. In 13.05 Advanced Thanatology, one of the possible deaths Billie lists off for Dean is a heart attack.
• Billie scrapes her scythe along the wall as she stalks Dean and Castiel in the Bunker. This was previously seen in 1.07 Hook Man as Jacob Karns stalks his victims and 7.18 Party On, Garth as the shojo stalked Lee Baxter.
• Castiel uses the angel banishing sigil to keep Billie at bay, drawing it with his own blood just as he first drew it to banish Zachariah in 4.22 Lucifer Rising. This also appears to be a nod to Bobby calling Death, the Pale Horseman, "the Angel of Death" in 5.10 Abandon All Hope..., further clarifying how the sigil can keep the current incarnation of Death at bay.
• Castiel's speech before being taken to the Empty is very similar to the one he gave while dying in 12.12 Stuck in the Middle (With You).
• When Castiel pushes Dean away from the portal to the Empty, he leaves a bloody handprint on Dean's shoulder, almost identical to the one left when Castiel first pulled Dean out of Hell in 4.01 Lazarus Rising.

15.19 Inherit the Earth

• When Dean takes the dog Miracle into his car, he breaks his own rule about no dogs in the car from 8.01 We Need to Talk About Kevin. He also broke it previously in 9.05 Dog Dean Afternoon when he lets the Colonel ride in the Impala during a case, though he barfs in the backseat.
• Michael said he was responsible for spreading the belief of the Abrahamic religions by having all the angels and former prophets over the past few millennia brand God's image all throughout the world. Amara previously compared the concept of religion to propaganda in 11.09 O Brother Where Art Thou?, encouraging these religions as monuments to his ego and promising to bring them to safety if they adored him. Kali also explained in 5.19 Hammer of the Gods that there were religions that were practiced long before the Abrahamic religions, including Hinduism where she is depicted.
• When Sam brings Chuck's Death Book to Michael, Jack is seen eating a nougat-filled chocolate bar. Jack says he's a fan of nougat in 13.01 Lost and Found and it has been mentioned throughout Season 13 – 15.
• Lucifer calls Dean imitating Castiel's voice and makes it seem like its a call from Castiel's phone to let him in the Bunker. This is similar to when Zachariah altered Dean's apology message to Sam in 4.22 Lucifer Rising to trick him into killing Lilith and release Lucifer from the Cage and when Anna Milton tricked John Winchester into going to the auto shop to lure him out and kill him in 5.13 The Song Remains the Same.
• When Lucifer kills the reaper Betty, she becomes the new Death, like Billie did as revealed in 13.05 Advanced Thanatology following her death in 12.09 First Blood. Death's Scythe even gains another updated appearance.
• Lucifer calls Jack "buddy" like he did previously in 13.22 Exodus and 13.23 Let the Good Times Roll.
• Chuck makes Michael explode and beats Sam and Dean to a pulp much like how Lucifer smote Castiel on a subatomic level and whaled on Dean in 5.22 Swan Song.
• Jack uses his powers as a walking black hole for divine energy, to steal Chuck's powers, making him the new God. Castiel did something similar in 7.17 The Born-Again Identity with Sam and his psychosis from his time in the Cage by shifting it from Sam's mind to his own. Jack only previously displayed such powers when he lent his power to Castiel to kill Dagon in 12.19 The Future.
• Castiel's and Jack's names are seen carved on the Bunker table below Mary's initials.
• At the end of the episode, we see a montage of scenes from multiple previous episodes.

15.20 Carry On

• The Winchesters once again use information in John's Journal to help them solve a case much as they often did in the earlier seasons.
• Sam uses dead man's blood bullets, which is one of the specialty bullets used by hunters over the years.
• While hunting the vampires, Sam and Dean encounter and kill Jenny from the Winchester brothers' very first vampire hunt in 1.20 Dead Man's Blood. Jenny was a young woman who was turned into a vampire by Kate after her lover Luther lets his nest kill and feed on Jenny's boyfriend. She and Kate escaped together after John Winchester killed Luther with the Colt. Dean comments on their history to the other vampires.
• The vampire fight occurs in a barn much as the Winchesters' first fight with Luther and his nest did.
• Dean's death mirrors Sam's first death from 2.22 All Hell Breaks Loose: Part Two as both brothers are stabbed in the back, with the other brother seeing blood on their hands from the wound and declaring they would find a way to save the other. Dean also tells Sam, "Come here. Let me look at you" during both death scenes.
• Sam and Dean's exchange as Dean is dying is verbatim from 1.01 Pilot, when Dean asked for Sam's help in finding their father. Dean even mentions when he picked up Sam to find John after dispatching Constance Welch the Woman in White. He admits he waited by Sam's dorm room for hours wondering if Sam would either tell him to get lost or die or what he would've done if he didn't have his little brother.
• Sam quitting hunting after Dean's death echoes what he told Charlie Bradbury in 10.18 Book of the Damned.

"This is my life. I love it. But I can't do it without my brother. I don't want to do it without my brother. And if he's gone, then I don't..."

• Dean and Bobby meet in Heaven outside of Harvelle's Roadhouse where they share a beer. Before the Winchesters burned his flask in 7.23 Survival of the Fittest, Bobby expressed hope to see them again in Heaven after they die. In addition, in 7.19 Of Grave Importance, after learning that Bobby stuck around as a ghost, Dean commented that Bobby could be in Heaven drinking beer at Harvelle's instead.
• Dean mentions Bobby being locked up in Heaven's prison for five years after helping Sam and Castiel free Metatron in 10.17 Inside Man, though Bobby tells him that Jack released him as he was making Heaven into what it was always meant to be.
• Castiel has been killed six times, as well as revived, throughout his 11-years:
  • Killed once by Raphael in 4.22 Lucifer Rising.
  • Killed twice by Lucifer in 5.22 Swan Song and 12.23 All Along the Watchtower.
  • Killed once by the Leviathans in 7.01 Meet the New Boss.
  • Killed once by the reaper April Kelly in 9.03 I'm No Angel.
  • Killed once by the Cosmic Entity in 15.18 Despair.
  • Revived three times by Chuck in 5.01 Sympathy for the Devil, 5.22 Swan Song, and 7.17 The Born-Again Identity (after months of amnesia).
  • Revived once by Gadreel in 9.03 I'm No Angel.
  • Revived once by the Cosmic Entity in 13.04 The Big Empty.
  • Revived once by Jack in 15.20 Carry On.
• Bobby mentions to Dean that Rufus Turner is in Heaven as well as John and Mary Winchester.
• Bobby explained that Jack brought Castiel back from the Empty and they made reparations to Heaven, no longer isolating each individual soul in their memories as was seen in previous seasons, but tearing down the walls and making Heaven into a more peaceful version of Earth.
• The Impala in Heaven has the original Kansas license plates KAZ 2Y5 from 1.01 Pilot to 2.19 Folsom Prison Blues, before they were replaced with Ohio plates CNK 80Q3 in 2.20 What Is and What Should Never Be after escaping from prison in Little Rock, Arkansas, following a ghost case.
• Amongst the pictures in Sam's house are many seen in previous seasons. The biggest is a picture of the entire Winchester family from 14.13 Lebanon. From left to right the pictures are of:
  • Sam and Dean (first seen in 10.03 Soul Survivor)
  • Mary Winchester (first seen 14.18 Absence)
  • Young Dean Winchester II
  • Dean, Mary, and Sam (first seen 14.19 Jack in the Box)
  • Young Sam and Dean
  • Sam and Dean (first seen 10.03 Soul Survivor)
  • Dean, Bobby, and Sam (first seen 10.03 Soul Survivor)
  • Young Dean II
• Sam left the Impala in his garage under a tarp. Dean did the same thing while he was living with Lisa and Ben Braeden in 6.01 Exile on Main St. and 6.02 Two and a Half Men after he retires from hunting for a year when they stopped the Apocalypse.
• Dean Winchester II has an anti-possession symbol tattoo on his arm.
• Dean's death and Sam's life after it are an echo of what Dean told Sam in 8.14 Trial and Error, where Dean tells Sam he will live a long life into old age with children and grandchildren.
• Sam dies of old age in the distant future, echoing what Dean said to Sam in 8.16 Remember the Titans after Prometheus's funeral pyre, that Sam is going to live a long life and will one day die of something normal like a heart attack rather than supernatural causes.
• Much like when Castiel told Dean he could find Sam by following the road in Heaven in 5.16 Dark Side of the Moon, upon arriving in Heaven, the first thing Dean does is drive until he meets up with Sam. Previously, Castiel calls it the Axis Mundi: a path that runs through Heaven which is seen differently by each soul in Heaven. For Dean in both cases, it's a "two-lane asphalt", though it starts off as a dirt road outside the Roadhouse until he drives into the woods and eventually reaches the bridge.
• Dean's death on a random vampire hunt can be tied back to 5.16 Dark Side of the Moon. In the episode, Ash reveals that Sam and Dean have both died "more than anyone I’ve ever met", but were always sent back with their memories wiped by God or the angels. With Chuck no longer in the picture, and Jack's proclamation to remain hands off, Sam and Dean no longer had any close calls or special protections from fatal injuries as their story now belonged to them. Dean makes peace with his death, as dying on the job was considered to be the best way to go in his opinion back in 12.06 Celebrating the Life of Asa Fox.

Meta References

Detail of Becky's Supernatural merchandise

• 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.
• Castiel is able to heal Sam's wound and mend his shirt. In Eclipse Magazine 2009, Misha explained: “Not only can Castiel heal the human body he’s possessing, but he has magical clothes mending abilities as well.”
• In 15.04 Atomic Monsters, we find Becky is still a Supernatural fan, writing fanfic and making miniatures. The Supernatural merchandise in Becky's house was a combination of commercial Supernatural merchandise, items made by fans, and some things made for 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 EyeCon in September 2008 by by Sandra Echeverri (@Sanpao19).
• Becky's notes about Chuck's new manuscript in 15.04 Atomic Monsters 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 that the story has low stakes cause Chuck to write a new dark ending, which is mirrored in the episode when he disintegrates Becky and her husband. Throughout the series, there have been multiple episodes which tackle meta nods of several kinds.
• In 15.07 Last Call, Lee Webb quips that Dean can't just lip-sync to "Eye of the Tiger" when no one's watching. This is a reference to the Jensen Sings outtake for 4.06 Yellow Fever where Jensen Ackles lip-syncs to "Eye of the Tiger."
• In 15.10 The Heroes' Journey, the Winchesters and Garth talk about how Sam and Dean are the heroes of the story while Garth is just a special guest star or a recurring character and not a main hero. Garth says he's fine with that, as he believes being the hero sucks because their lives are hellish until they win, which they always do eventually.
• In 15.12 Galaxy Brain, while preparing to destroy all of the alternate universes, God say He needs less of the "failed spinoffs." The Bad Place was an alternate universe created for the Wayward Sisters spin-off and is destroyed in the episode. Another planned spin-off was Supernatural: Bloodlines. Supernatural had aired one spin-off, the Ghostfacers Web Series, which only lasted one season.
• The similarity in the events of 15.20 Carry On to 3.11 Mystery Spot is a possible nod to Jared Padalecki mentioning the team's consideration to end the show at Season 3. In the Nerd HQ at Comic Con 2011, he cited 3.11 Mystery Spot as a possible series finale (along with a possible movie) due to the Writers Guild of America Strike back in 2007-2008 since it was the last episode made before the strike.