Alternate timelines are the result of changes in the space-time continuum, created usually via time travel. They differ from Alternate Universes in that they are apparently rewritten versions of the same universe, resulting in the new timeline overwriting and essentially destroying the original.

Rules

People and entities that are subjected to this changes will not remember their previous lives after the transition from the old reality to the new. However, those who are responsible for the change, can in some cases remember the previous timeline, as it was the case with Castiel and Balthazar. Entities like Atropos are immune to timeline alterations.

Changing the timeline can sometimes create temporal paradoxes, where beings and objects from a previous timeline can still paradoxically exist in the new one for a short period of time. An example of this was when John was transported from 2003 to 2019, Sam and Dean Winchester continued to exist as themselves, despite their lives also being affected and Mary Winchester was still alive, despite the events leading up to her resurrection never happening. However Sam theorized that this won't last long and that Mary will just fade away, while he and Dean will become this new timeline's version of themselves.

Alternate Timelines so far

The End: an alternate timeline where Sam said "Yes" to Lucifer, while Dean refused to say "Yes" to Michael. The fallen archangel succeeded in winning the Apocalypse and conquering the Earth. This timeline was erased when Sam dragged both Lucifer and Michael in the Cage.

My Heart Will Go On: an alternate timeline that came about when Balthazar prevented the Titanic from sinking on its maiden voy
Alternate Universe (My Heart Will Go On) Ford Mustang

Dean's car in a new timeline, a mustang.

age, on orders of Castiel who needed more souls for his war against Raphael. Ellen and Jo are alive, Sam and Dean drive a first generation Ford Mustang and thousands of people who previously didn't exist are alive and walking. This timeline was erased by Balthazar on Castiel's orders.

Family Feud: an alternate timeline which was created when Abaddon kidnapped Gavin MacLeod , thus preventing him from sailing with The Star and drowning in 1723. As a result, he was not present when his fiancé Fiona Duncan came looking for him. Fiona was brutalized by the members of the ship and became a vengeful spirit that murdered several teachers centuries later (because her own teacher, that was on board, encouraged that instead of helping her). This timeline was erased when Gavin returned back to the past.

Lebanon: an alternate timeline where John Winchester disappears in 2003 and is transported to 2019 as a result of Dean using the Baozhu. As a consequence, Mary stayed dead, Dean continued to be a hunter (and a wanted criminal, due to his uncovered hunting activities) and Sam became a successful corporate lawyer. Castiel and Zachariah remained in Heaven's service and the Apocalypse never happened. This timeline was erased when John decided it's best to return back to his time.

The Trap: an alternate timeline where the Winchesters and Castiel locked away God. As a result of God being locked away, darkness prevailed in the world and the monsters began running rampant with the Winchesters friends falling one by one to the monsters. Castiel, after taking on a Mark to seal away God, went nuts and had to be locked in a Ma'lak Box. Sam and Dean are turned into vampires on a hunt gone wrong and come up against Jody Mills and Bobby Singer on December 9, 2022. Dean kills Jody while Bobby kills Sam, though the ultimate fates of Bobby and Dean are unknown. This timeline is erased when Sam, believing that God was telling him the truth when he showed Sam the future, chose not to trap God.

Characters from Alternate Timelines

Appearances

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