Professor Sebastian leads a specialized scientific unit within Team Rocket's research division, commanding agents Attila, Hun, and Tyson clad in grey uniforms. These agents execute his experiments and ensure field security. His core function is developing advanced technological devices for Team Rocket's objectives.

He personally introduces the Miracle Crystal to Attila and Hun in "The Legend of Thunder!" special. This device attracts and absorbs electrical energy, specifically designed to capture Electric-type Pokémon, including the Legendary Raikou. Sebastian oversees its deployment and monitors the operation. He later invents the separate "Evolution Inducement Ray," intended to force Pokémon evolution.

Physically, Sebastian is notably shorter than most adults. He sports a triangular goatee and a distinctive white streak in his otherwise dark hair. His heavily lidded eyes and frequent subtle smile project a consistently calm, self-assured, and collected demeanor. His attire consists of a closed off-white jacket with a high collar and dark blue accents, paired with white pants and black dress shoes, differing from standard lab coats.

He maintains a hierarchical rapport with subordinates that varies. Tyson shows clear reverence, while Attila and Hun interact more casually. English adaptations imply a prior relationship with Hun, distinct from the original portrayal. Sebastian directs large teams of scientists during operations, including the capture of the Red Gyarados and the Miracle Crystal project. His experiments often involve manipulating powerful or rare Pokémon, extending to a later movie cameo where he conducts electrical experiments on a captured Rayquaza.

Despite overseeing the capture of Raikou, Red Gyarados, and Rayquaza, he never personally engages in Pokémon battles, relying entirely on his agents for combat and protection.