Seeking revenge after his wife Mary was killed by the demon Azazel, John Winchester became a hunter and raised his two sons to fight the supernatural.

Morgan was also filming episodes of Grey's Anatomy while the first season of Supernatural was under production, and future appearances of the character were hindered by his busy schedule.

[5] John left high school to join the Marine Corps, eventually attaining the rank of corporal and receiving many medals for his service in Vietnam.

Dean later watches John being killed by Azazel, though the demon then resurrects him in exchange for Mary's permission to enter her house in ten years.

[7] When the angel Anna Milton travels back in time in the fifth-season episode "The Song Remains the Same" to prevent the births of Sam and Dean, John agrees to serve as a temporary vessel for the archangel Michael to stop her.

[9] He took his sons with him during his travels, but often left them alone in motels for long periods of time during his hunts,[11][12] leaving Dean with instructions to "shoot first and ask questions later" while watching over Sam.

[9] Twenty-two years after Mary's death, John disappears while on a hunt, forcing Sam and Dean to reunite in an unsuccessful attempt to find him.

[15] When vampires murder his old mentor and steal the Colt—a mystical gun capable of killing anything—John teams up with Sam and Dean in "Dead Man's Blood" to retrieve it.

John is captured after trying to give her a fake gun,[17] and reveals himself to be possessed by Azazel when the brothers come to his rescue in the first-season finale "Devil's Trap."

[23] In the show's 300th episode, "Lebanon", Sam and Dean accidentally draw John from 2003 into their timeline when they acquire a Chinese pearl that grants the owner's greatest wish.

However, John being drawn into the future begins to cause changes to history; Dean and Sam see 'Wanted' posters identifying Dean as a serial killer, Sam is now an internet celebrity who is also the head of his own law firm, and Castiel is still a loyal servant of Heaven and the living Zachariah who attack the Winchesters to investigate the disruption to the timeline, although the Winchesters are able to kill Zachariah and banish Castiel.

While the Winchesters debate about their next course of action before the new timeline changes them as well as everything else, they are eventually forced to send John back to his time believing that his trip to the future was just a dream, but he departs accepting his fate and assuring Dean and Sam that he understands their decision, also adding that he is proud of the men his sons have become.

In the next episode, the angel Dumah confirms John and Mary are sharing a Heaven together and threatens to end their peace with a snap of her fingers to force Castiel to comply with her demands.

Introduced to the world of the supernatural, John quickly becomes enamored with both hunting and Mary, helping her to find the box in a New Orleans cemetery and slaying a loup-garou watchdog.

Now aware of the dangers of the world, John decides to become a hunter, telling his mother that he feels that he was born for "saving people, hunting things," which would later become the basis of the Winchester family's motto.

The Bori Baba case brings them back together and they make amends, parting amicably with Betty returning his engagement ring and asking to remain friends.

Actor Jeffrey Dean Morgan deemed John a "tormented soul," motivated by an "equal combination of revenge and protecting his sons.

Kubicek also suggested that John became involved in Adam's life to achieve "some level of normalcy" as a father, an opportunity he had previously lost following the death of Sam and Dean's mother.

[29] Though he survives in the final version of the pilot, the writers decided halfway through production of the first season that John did have to die, as they believed his separation from his sons "split the show" by having him away "doing more interesting things than the boys are doing.

"[30][31] Kripke also felt that John kept Sam and Dean away from the "front lines," his death being required to allow the brothers to "explore, investigate and confront the yellow-eyed demon directly."

The writers initially intended for John to die in the car accident in "Devil's Trap," but they ultimately postponed his death to prevent the finale from becoming too dark.

[32] Following the character's eventual escape from Hell, executive producer Ben Edlund stated that even the writers are unsure of where John's soul ended up.

[25] During production of Supernatural's first season, Morgan was also working on the shows Weeds and Grey's Anatomy, so he was often traveling back and forth between Los Angeles and Vancouver, British Columbia.

"[38][39] The scheduling conflict has continued into the sixth season of Supernatural, with executive producer Robert Singer revealing that the writers had considered bringing the character back in the alternate reality episode "My Heart Will Go On" instead of Ellen Harvelle, but due to concerns that they would not be able to secure Morgan's return, they ultimately chose Ellen for the deceased character they would have (temporarily) return in the episode.

"[42] Williams praised Matt Cohen's performance of a younger version of the character in the time-travel episode "In the Beginning", believing that he "did an excellent job at portraying a more innocent John Winchester than we've ever seen before".

[46] While Brian Tallerico of UGO enjoyed Morgan's performance, he was happy that the character was killed off because John's presence made Sam and Dean into "followers" that were "merely existing in the wake of their father".