Time travel in Supernatural has been brought about by supernatural beings – primarily angels, and on one occasion a god. Henry Winchester and Abaddon both have used a blood spell to travel through time.
When time travel is used in a story it raises the issue of how that time travel may affect events occurring before or after it. Many conundrums are raised – collectively known as temporal paradoxes.
The time paradox was discussed in the writer’s room with a light touch because I think it gave us all headaches. Like for instance I have a theory about this episode that I don’t think we even talked about that this was a closed ended loop that Dean ALWAYS goes back in time and instigates the events that happen in this episode which caused Sam and Dean to be put on this path which caused them to run into Castiel who sent Dean back in time.
Jensen called us to say,
“I’m the one who talked my dad into buying the Impala? But I don’t understand that because if I hadn’t have gone back in time he wouldn’t have had the Impala.”
Again it’s a real mind-bender concept and we had to talk it through – it's funny the difference between Bob Singer and I proceeded to talk him through,
“Well there’s this time loop and in my mind it’s this closed circle and he’s always going back –”
And you know all these concepts that I really don’t understand about the inevitability of fate and time travel and then Bob takes a beat and – I love it, it’s perfect timing – he just takes a beat and says in this typical voice,“You got no problem with the demons but you got a problem with this?”
Eric: There was this whackadoodle notion that Ben and I came up with, where Future Dean had already gone through the experiences as Past Dean, where Future Dean was like "I know why you're here, because five years ago I went through the same experience … and every line you're about to say I've already said it. And time is cyclical!"
And we were congratulating ourselves for being so smart...We showed it to Bob – and it’s a perfect model of why Bob is so invaluable to Supernatural ... and he's like "What the hell is this?" And we're like "You see it's cyclical, time is cyclical..."
Ben: Do you remember we would come to his office and we would draw pictures of it.Eric: Yeah, we were literally drawing a diagram of the nature of time and time travel in Bob's office. And he gives you this wonderful dry look and he's like "You'll be drawing that for the audience?"
In Supernatural, the rule has been that the time line is fixed, traveling to the past will not alter events that have already happened. However once the Apocalypse was averted, the rules were changed, allowing for the past to be altered as shown in 6.17 My Heart Will Go On, where Balthazar prevents the Titanic from sinking, and this has ramifications throughout the subsequent years.
Castiel sends Dean back to Lawrence in 1973. Dean tries, and fails, to kill Azazel. Castiel tells him the purpose of the trip was for Dean to learn how the involvement of the Winchester family with Azazel began, and hopefully help Dean, and Heaven, work out what his ultimate endgame was – and Sam's role in it.
Zachariah creates a future where Sam and Dean are no longer hunting together and haven't been for five years. It's the year 2014 and most of the population are either dead or have become zombies due to the Croatoan virus. Originally conceived a time travel piece, the episode ended up presenting the 2014 future as an alternate universe constructed by Zachariah.
On Heaven's instruction, Anna goes back to 1978 to kill John and Mary Winchester, in order to stop Sam from ever being born. Castiel takes Sam and Dean back to stop her, and is severely weakened by the effort. Michael ends up intervening to save John and Mary, erasing their memories of the events.
This episode involves both time travel and an alternate universe.
Castiel orders Balthazar to stop the so that there would be 50,000 souls in existence that otherwise wouldn't be (the descendants of passengers) in order to use the souls to gain power in his fight against Raphael. The act causes a cascade of changes through history:
- Dean drives a Mustang which has the original plates the Impala had – KAZ 2Y5.
- The Impala line of cars was not produced.
- Ellen and Jo are alive.
- Ellen and Bobby are married and Singer Salvage Yard is called B & E Scrap Yard. Bobby's house appears neater than usual.
- In 2.17 Heart we learned that Sam knew Dean always played 'scissors' when they did rock, paper, scissors, so Sam always won. Here Sam loses, although Dean still throws scissors.
- In the travel agency we see Cuba is a resort island destination – "America's Favorite Holiday Destination" – and Detroit was voted "America's Top City."
- Celine Dion is a "destitute lounge singer somewhere in Quebec."
- Cas transports Sam and Dean to "White Russia." This is an old term for Belarus and may be a hint that the Russian revolution of 1917 that lead to the formation of the Soviet Union, didn't occur.
- Obviously the movie the Titanic was never made!
Eventually, in order to save Sam and Dean, Balthazar is forced to return to the past and unsink the Titanic, changing everything back though Castiel makes sure Sam and Dean remember what happened.
Dean and Sam get Castiel to send them back to 1861 after reading that Samuel Colt shot a phoenix, the ashes of which they believe will kill Eve. Meanwhile Castiel is weakened after being attacked by Rachel and must draw on power from Bobby's soul to bring them back. When Sam and Dean are pulled back to the present day without the ashes, they think the cause is lost, but then a courier arrives. He delivers a package to Sam sent 150 years ago by Samuel Colt. It contains Sam's phone – and a bottle containing the ashes of the phoenix.
Chronos, the God of Time, can travel through time by taking energy from three humans. Dean charges him as he is attacking a man and is pulled back in time with him to 1944. Chronos evades Dean, but his killings in this year have attracted the notice of hunter Eliot Ness, who teams up with Dean.
In the present, Sam and Jody Mills find a spell to summon Chronos to their time and location. When the now elderly Lila Taylor reveals that she witnessed Chronos throttling Dean in 1944, and that the clocks stopped at 11:34 that night, Sam and Jody are able to summon Chronos while he is attacking Dean, bringing both of them to the present. Sam stabs Chronos with the stake that came with them. Chronos, dying, tells Sam that his future is full of black ooze, covering everything.
In 1958, desperate to escape the demon Abaddon, Henry Winchester casts a spell made with a blood sigil, which involved an angel's feather, tears of a dragon and a pinch of the sands of time to find his son John Winchester in the future to help him protect a mysterious box from the secret order known as the Men of Letters. Henry instead finds Sam and Dean in 2013 and is confused as to why he wasn't taken to John. Before he can explain what is going on, Abaddon follows him through the portal and proves immune to Ruby's knife, forcing them to flee. Henry is horrified to learn that John is dead and explains who he is and why he is there, though he doesn't like working with hunters. After Sam learns what the box is from a survivor of the order, Abaddon reveals herself and captures Sam. At the same time, Henry, after learning what happened to John and that he apparently never made it back to his time, tries to travel back to an hour before Abaddon arrived so he can change things but is foiled by Dean. The two are forced to make a deal with Abaddon to save Sam's life, but it is actually a trap: Henry shoots a devil's trap-engraved bullet into Abaddon's head, binding her in place and to her meatsuit. Dean then decapitates her with the intention to cut her up into little pieces and bury her in concrete to forever trap her. However, Henry is mortally wounded in the fight and dies, never to return to his own time.
Using the blood spell Abaddon travels back in time to 1723, to Leith, Scotland. There she finds Crowley's son Gavin MacLeod, and brings him back to the present day to use as leverage to get Crowley to help her kill Sam and Dean.
After Abaddon is killed, the Winchesters tell Crowley they must return Gavin to his own time, or it may have an unknown ripple effect on events. Crowley protests, knowing Gavin is destined to die soon in the past. He manages to escape with Gavin. He leaves Gavin to live in the present day, saying that they mustn't ever see each other again.
Sam and Dean also travel through time in the novel Supernatural: War of the Sons, when renegade angel Don -- full name Abaddon -- sends them back in time to New York 1954. He claims that he wishes to help them recover the 'War Scroll,' a scroll containing a battle plan that would allow the brothers to defeat Lucifer, but when the Scroll is revealed to contain only the names of the angelic bloodlines and the humans who will be their vessels, Dean and Sam refuse to use it, realizing that Don's true role was to attempt to convince the brothers to accept their role and allow the Apocalypse to proceed. Having returned to their time, Dean and Sam trick Don into attracting the attention of the other angels, allowing the angels to kill him while Castiel takes them to safety.