Seviper debuted in the Advanced Generation episode "A Tail with a Twist," displaying fierce aggression by defeating Ash's Treecko. Jessie captured it after an intense struggle where Seviper evaded multiple Team Rocket traps; she subdued it physically after it damaged her hair. Instantly becoming Jessie's primary battler, it fought consistently alongside James's Cacnea in Hoenn and later his Carnivine in Sinnoh. Its battle style utilized venomous attacks and strategic bladed tail strikes, reflecting its species' natural weaponry of deadly venom and a sharpened tail. Under Jessie's alias "Jessilina," Seviper performed in Pokémon Contests. Its first appeal in "All Things Bright and Beautifly!" failed due to Jessie commanding unusable moves. Later contests showed better coordination, like emerging dramatically from Carnivine's mouth in the Daybreak Town Contest. During battle rounds, it teamed up with Jessie's other Pokémon, including Dustox and Yanmega. Collaborative techniques included propelling Dustox's Poison Sting with Poison Tail for greater force, merging Haze with Yanmega's Sonic Boom into a swirling energy wave, and enhancing Poison Tail with Yanmega's Silver Wind to fire purple energy projectiles, showcasing adaptability beyond standard battles. Seviper displayed fierce loyalty to Jessie alongside inherent aggression, particularly triggered by encounters with wild Zangoose. This instinctive species rivalry caused it to disobey orders during a clash with a Trainer's Zangoose in "ZigZag Zangoose!," initiating a solo battle where it initially dominated before losing a rematch. Despite this defiant streak, it showed concern for Jessie after contest mishaps, indicating a bond deeper than simple obedience. Jessie eventually left Seviper at Team Rocket headquarters when departing Sinnoh, as its status as non-native to Unova risked drawing unwanted attention.