Peppercat is a cat-type Medabot who serves as the partner and leader Medabot of Samantha, the strong-willed head of a group known as the Screws. A recurring presence throughout the story, Peppercat is one of the earliest Medabots showcased in the series, taking part in one of the first Robattles shown, a battle against the student council's Dr. Study. She is an upgraded version of the earlier Magentacat model and carries the model number CAT-3120 in the anime. Her design follows a feline pattern, with a yellow forehead marked by a screw-like decoration set in a long black recess, a wire-like tail, thicker legs, plug endings along the hem of her skirt, and sharp clawed hands on red-and-white arms. A visor attached to her forehead can be pulled down over her face, though this feature appears mainly in related media rather than as a regular tool in the story.

In terms of ability, Peppercat is built for speed and disruption. Her head and both arms generate electric thunder attacks that can briefly stop an opponent's movements, leaving the target unable to defend or act for a short time, while her bipedal legs, named Quick Alert, grant her strong agility, particularly over grassland and forest terrain. These traits make her a fast, debilitating frontline fighter who can close distance quickly and disable targets so that allies can follow up. Her parts are known as Light Circuit for the head, Light Jab for the right arm, Light Blow for the left arm, and Quick Alert for the legs, and she runs on a Queen type medal that complements her part set and combat style.

Personality-wise, Peppercat comes across as a confident and competitive fighter who takes clear pride in her performance in Robattles. She is dependable in battle and more effective than her teammates, outperforming the slow Totalizer and Cyandog, later upgraded to Krosserdog, whose Monkey medal is not compatible with his parts. Her battle attitude has a playful edge, with a tendency toward taunting opponents, as reflected in one of her battle lines in which she tells a disabled opponent to enjoy feeling numb for a while. She is a loyal and capable companion to Samantha, and the two work well together as a team.

Within the larger group dynamic, Peppercat stands as the most capable of the Screws' Medabots, frequently shouldering the combat duties and serving as Samantha's leader Medabot in tournament settings. Her role in the story is primarily that of a recurring rival and supporting combatant, appearing in tournament stages and later random encounters and providing a strong opponent for the main characters to measure themselves against. Her development is tied to her partnership with Samantha rather than to any major personal arc, and she remains a steady, reliable presence among the recurring Medabots throughout the series.