Peach is a robotic dog companion to Ken Kitazawa and Professor Utonium. Originally non-sentient, he gained intelligence and speech after accidental exposure to a white Chemical Z ray. This occurred during an incident where Peach knocked a pastry into a vat of Chemical X, creating Chemical Z, which dispersed across Tokyo City (New Townsville in the English dub) as black and white rays.

He exhibits a kind, persistent, and occasionally stubborn personality, displaying loyalty to Ken and the Powerpuff Girls Z as a supportive figure. Peach experiences emotions like affection, including romantic interest in Sapphire (a female dog), and frustration or anger when deceived. He serves as comic relief through interactions and misunderstandings, particularly involving romantic pursuits or challenges.

Visually, Peach resembles a cream-yellow robotic dog with brown ears, a violet nose, and a yellow collar featuring a bone-shaped tag. His design remains consistent.

His primary abilities include sensing Chemical Z residue or "auras" (recorded in his systems for reference), detecting individuals affected by black or white Z-rays, and identifying disguised entities, though this is hindered by heavy cosmetics. His bark activates the Powerpuff Girls' transformation sequences and restores their depleted powers. In combat, he demonstrates unexpected skills like karate using his collar's bone.

Functionally, Peach acts as an alarm system, alerting the team to threats and facilitating their superhero duties. He shares a close bond with Ken, accompanying him in scientific endeavors, and views the Powerpuff Girls as older sisters. He temporarily joined Ken and Professor Utonium as part of the "Powerpuff Boys Z" during one episode when the girls were absent.

Across the series, Peach maintains a consistent role without major arcs, though his relationships and minor contributions to resolutions are recurring elements. His background and traits are adapted in the manga.