Poochie, originally named Peach in Japanese, is a robotic dog created by Professor Utonium as a companion and playmate for his young son, Ken Kitazawa. His origin is tied to the series' central Chemical Z incident. During an experiment where Ken used Chemical Z to destroy an iceberg threatening Tokyo City (New Townsville in English), an explosion scattered black and white Z-rays. Bathed in a white Z-ray, Poochie gained heightened intelligence, human speech, and specialized capabilities, transforming from an ordinary robot into a sentient being crucial to the main plot.

He serves a pivotal operational role for the Powerpuff Girls Z team. His advanced olfactory system detects and identifies individuals or objects affected by black Z-rays, white Z-rays, or Him's black particles, storing scent signatures in his data banks. This ability fails against targets wearing heavy cosmetics, as seen with Sedusa. Poochie can recognize individuals despite complete appearance changes. His signature bark triggers the Powerpuff Girls Z's transformation, either in person or remotely. Though later modifications allowed self-initiated transformations via compacts, Poochie retained the critical ability to restore their powers when depleted, essential for recharging them during energy-draining battles.

Poochie exhibits kindness and loyalty towards Ken and the Powerpuff Girls Z, viewing them as family. He demonstrates determination, notably in an episode where he develops romantic feelings for Sapphire (Princess Morbucks' cat). He deliberately loses a card game to win her affection. Discovering her malicious intent leads to heartbreak and anger, showcasing emotional depth, capacity for betrayal, naivety, and growth. He also participates in auxiliary heroics, briefly forming the "Powerpuff Boys Z" with Ken and Professor Utonium when the main team is grounded. His interactions reinforce his supportive and morally grounded role.

His design features a cream-yellow body with brown ears, a violet nose, and a yellow collar with a bone-shaped tag, distinguishing him from organic dogs while maintaining a familiar canine appearance. Symbolically, he fuses elements from the original series, replacing both the Talking Dog and the Powerpuff Hotline, with his bone symbol as his consistent identifier. Trivia notes his favorite food is dumplings. As a digital entity granted sentience by the Z-ray, Poochie remains the series' sole robotic dog capable of human speech. His character maintains a steady presence as a reliable support figure and emotional anchor for Ken throughout the series.