Characterization
With her father dying on a hunt when she was just a child, Jo treasures his pure iron knife engraved with his initials, and carries it around with her. Her desire to be a hunter stems from the longing to feel connected to him. She attended college at one point, but eventually dropped out because she was considered just "a freak with a knife collection". 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. However, Jo grows throughout the season as she rebels against her mother by running away to be a hunter, which Kripke felt made her harder and tougher. 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. Tal commented, "She fought and risked her life and stayed there as bait. It took a lot of guts."
The actress noted that Jo matures during her hiatus. Having found out the hard way that "banter doesn't always work", she becomes quieter and "not as mouthy". The character "called the shots" in her final appearance, and was the "bigger person" by forcing everyone to accept the reality of the situation. After years of hunting together, the relationship between Jo and Ellen also develops; Tal came to view them more as equals rather than daughter and mother. Although Jo's feelings for Dean remain the same, Tal liked the fact that she does not easily give in to Dean's advances in "Abandon All Hope...". She believed that Jo resists her urge to "go crazy " due to the dire circumstances, which "gave it a little more meaning".
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