Jessie caught a Wurmple in All in a Day's Wurmple, as did May. The chance encounter occurred on a tree branch after Team Rocket was blasted off yet again; Jessie noticed Wurmple nearby and simply threw a Poké Ball at it. Jessie quickly grew infatuated by her Wurmple, often spoiling it with her attention and referring to by cutesy nicknames.
In Which Wurmple's Which?, both Wurmple were temporarily switched with one another, but eventually, they were returned to their proper Trainers by the end of the day.
In A Corphish Out of Water, Jessie's Wurmple evolved into a Cascoon while May's evolved into a Silcoon; Jessie believed hers was a Silcoon as well. Later, in Seeing is Believing!, Jessie's Cascoon evolved into a Dustox, soon after May's Silcoon evolved into Beautifly. Though Jessie was initially disappointed that she did not have a Beautifly, she came to adore her new Dustox almost immediately. In the Japanese version, she called her Dokucale-chan on more than one occasion. In the English dub, Jessie often called her Dustox-Dear, and when she would throw her Poké Ball, she has also refer to as "my dear Dustox".
Dustox was Jessie's primary Contest Pokémon. She was used in the Fallarbor Contest in Come What May and then the Verdanturf Contest in Disguise Da Limit. Jessie attempted to enter her in the Rubello Town Contest in A Fan with a Plan, but Jessie did not have a previously obtained Ribbon needed for entry.
In That's Just Swellow, James used Dustox as his Pokémon in the Crossgate PokéRinger competition. Dustox defeated May's Beautifly, but she was then defeated at the last minute when Ash's Taillow evolved into a Swellow.
In A Stand-Up Sit-Down!, Jessilina decided to face off against Dawn in order to practice for the Hearthome Contest. However, it was Zoey who accepted the challenge. Jessie used the combination of Dustox and Seviper and her idea was to make Dustox use Poison Sting and then to make Seviper use Poison Tail on Dustox's Poison Sting, making it spin and adding extra-power to it. Brock even said that that was a smart combination. However, that didn't work as Zoey's Glameow countered with Iron Tail, making the combination go to the other side. Zoey's Shellos then used Mud Bomb, breaking the combination of Poison Sting and Poison Tail. Dustox and Seviper were then both easily defeated by Zoey's Glameow.
In Team Shocker!, Dustox was used in the Solaceon Town Pokémon Contest. During the Performance Stage, she used Whirlwind to lift Jessie off the ground, leaving the crowd astounded. She kept Jessie floating for a while and then used Psybeam to create a thick green smoke which covered the entire stage. When the smoke was cleared, it revealed Jessie and Dustox smiling and posing before the audience. The performance was well-received by the panel of judges and, when the results were announced, Jessie appeared among the Coordinators advancing to the Battle Stage. There, Dustox was able to defeat her first two opponents to reach the finals, where she went up against Kenny's Prinplup. She managed to use Prinplup's techniques against him to win the battle, earning Jessie her first Contest Ribbon. Ever since, Dustox has been wearing Jessie's hair-ribbons that she wore in that Contest.
In Crossing Paths, during the Dustox Crossing, she fell in love with a Shiny Dustox owned by Austin. Jessie tearfully decided that Dustox had to go with the others, despite everyone's protests, but, since Dustox was loyal, she didn't want to. Seeing that Dustox was facing the same dilemma Jessie once was, about to throw away her chance of finding her true love to be with friends, Jessie had to shatter Dustox's Poké Ball to let her go. Dustox then went to live with other Dustox and start a family, giving Jessie the hope of finding her own soulmate.
In Our Cup Runneth Over!, Jessie said she would dedicate her performance in the Wallace Cup to Dustox, in her flashback. In Jumping Rocket Ship!, she appeared in Meowth's flashback.