Arbok first appeared in Pokémon Emergency! as an Ekans. It was used constantly by Jessie and eventually evolved into an Arbok in the episode Dig Those Diglett! along with James's Koffing after Jessie and James desperately wanted their Pokémon to evolve.
Arbok and Weezing seem to be both very emotional. This was first shown in Island of the Giant Pokémon, where they got very sad for being separated from Jessie and James, crying desperately, with Pikachu cheering them. In the end of the episode, when every lost Pokémon got reunited with their partners, Ekans and Jessie, along with James and Koffing, were happily crying, while Ash was only smiling with Pikachu, which may mean that Jessie's bond with Arbok is stronger than Ash's bond with Pikachu. It was also in this episode that it explained to Meowth along with James's Koffing "Pokémon do bad things because master bad. Pokémon not bad.". In Lights, Camera, Quacktion both Arbok and Weezing got depressed for being rejected as the main characters in the movie. It was only with Jessie's and James's help that they got over it. On their last appearance, in A Poached Ego, they were reluctant in leaving Jessie and James, and when they did, they strongly cried.
Jessie used Arbok as her main battling Pokémon throughout most of the series up until Advanced Generation, a role which has now been taken over by Seviper. Jessie also used it during the Princess Festival.
In A Poached Ego, Team Rocket found a poacher holding a herd of Ekans and Koffing captive in Hoenn. After freeing them, James and Jessie reluctantly ordered Arbok and Weezing to stay in the wild and guard their fellow Pokémon. The two Pokémon have not been seen since.
Jessie and Arbok shared a close bond, as demonstrated when Arbok refused to leave her at first and cried when it finally did.