Season 15 Callbacks

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

Returning Characters

• Amara
• Arthur Ketch
• Kevin Tran
• Rowena

Creatures and Spirits

• Constance Welch
• John Wayne Gacy
• Mary Worthington

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.

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 ago 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 killed by Mary Winchester.
• Francis Tumblety attempted to absorbed Kevin's spirit, the last time this act among ghosts had been see was with Whitman Van Ness in 7.19 Of Grave Importance.

Meta references

• 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.