Aspiring to be a hunter of supernatural creatures like her parents, she was introduced in the second season in order to explore a mother-daughter relationship in the hunting world.

[1] The brothers look for her mother Ellen at Harvelle's Roadhouse—a saloon frequented by hunters of supernatural creatures—after she leaves a voice mail message on the phone of their deceased father, John Winchester.

[1] Wanting to be a hunter like her late father, Bill, to feel connected to him, Jo slips away from the Roadhouse against her mother's wishes to help the brothers on a hunt in "No Exit", but they ultimately have to rescue her from a vengeful spirit.

An angry Ellen reveals to her that John's recklessness caused Bill's death,[3] which strains Jo's friendship with Sam and Dean.

Dean and Ellen arrive and, after a brief struggle, convince Jo and Rufus that War, one of the Four Horsemen of the Apocalypse, is responsible for making all the townspeople turn against each other by thinking that both sides are demons.

[8] Jo is mentioned but not seen in the sixth season episode "My Heart Will Go On", in which she is temporarily restored to life as a result of the angel Balthazar saving the Titanic from its destined sinking.

[9] She makes an on-screen return in the seventh season episode "Defending Your Life" as a ghostly witness called by the Egyptian god Osiris when he is judging Dean's guilt.

[10] Supernatural executive producer Robert Singer confirmed that the apparition was Jo's ghost and not an illusion created by Osiris.

[11] Series creator Eric Kripke initially described Jo as an "innocent girl who wanted to be a hunter" and who tends to look before she leaps; she is also "enthusiastic" and very "girl-next-door" in her approach to hunting the supernatural.

[13] However, Jo grows throughout the second season as she rebels against her mother by running away to be a hunter, which Kripke believed made her harder and tougher.

[12] Regarding her character's capture by a vengeful spirit in "No Exit", actress Alona Tal felt that Jo was a "badass" who handled the situation well.

"[17] With the character now a spirit in her seventh season appearance, Tal felt that Jo's death brought her "clarity" and "a different level of comfortability".

[11] However, series writer and co-executive producer Adam Glass felt that Dean still has "some real guilt" over Jo's death because the character feels that he "could have pushed [her] away from this life, not pulled [her] more into it.

"[11] Due to the father-son dynamics of the hunting world depicted in the series' first season with the Winchesters, the writers decided to explore a mother-daughter relationship.

I got what I wanted for Jo, which was respect.Kripke felt that she came across as more of a "girl-next-door" than the dangerous type of character Dean would be attracted to, like Sydney Bristow of Alias.

[21] The opportunity to return surprised Tal due to the character's negative fan reaction and the large time span since her previous appearance.

[16] Jo was one of many deceased characters the writers considered to have appear in the alternate reality of the sixth season episode "My Heart Will Go On", but they ultimately settled on Ellen.

Diana Steenbergen of IGN favored Jo from the beginning, deeming her "tough and direct, and also female, something the boys don't have a lot of in their lives right now".

[25] While Tina Charles of TV Guide was at first unsure about the character, she wrote that by the episode "No Exit," "Tal did step things up and kinda won me over."