Gatchan emerged from an angelic egg placed on Earth by the Galaxy God in prehistoric times, intended to halt human technological progress. This plan collapsed when Senbei Norimaki's time travel brought the egg to Penguin Village. Adopted by the Norimaki family, Gatchan received the full name Gajira Norimaki—blending "Gamera" and "Gojira"—but answers primarily to Gatchan. The character lacks physical genitalia and exhibits no defined gender, with references using both male and female pronouns. Communication occurs through unique sounds like "Pipokupipo" or "Koo pee pee poo," understood only by Arale Norimaki and later Turbo Norimaki.

Gatchan consumes and digests nearly any material except rubber, displaying a preference for metal—an instinct tied to the original divine mission of disrupting technology. Key abilities include firing Antenna Beam energy rays from head antennae for defense or play, flight via small wings, and absence of physical aging. Originally singular, Gatchan spontaneously underwent fission, wrapping in a cocoon and emerging as two identical entities collectively called the Gatchans. This replication trait is inherent, with future timelines showing up to eight coexisting Gatchans.

In *Dr. Slump & Arale-chan: Hello! Wonder Island*, Gatchan joins Senbei and Arale on a quest to Wonder Island for a love-potion ingredient, prompted by a videotape from Senbei's deceased father. The adventure underscores Gatchan's loyalty to the Norimaki family, contributing through flight and material consumption without direct combat.

Across media, Gatchan appears consistently alongside Arale. In *Dr. Slump* manga and anime, Gatchan engages in playful mimicry of Arale, dons costumes during games, and temporarily multiplies or transforms—including becoming a pig via Senbei's inventions or achieving a Super Saiyan-like state. A pivotal moment reveals the Galaxy God abandoning the plan to destroy humanity upon witnessing Gatchan's happiness with the Norimakis. *Dragon Ball* crossovers, like the General Blue Saga and *Mystical Adventure*, show the Gatchans aiding Arale in battles—firing Antenna Beams against foes such as General Tao and consuming metal objects like vehicles. *Dragon Ball Super* depicts them accompanying Arale to West City, where they inadvertently devour an entire building during a conflict.

Gatchan’s design features green hair, antennae, and infant-like proportions, inspired by Akira Toriyama’s sister’s newborn and elements from his unreleased *Ageha Town Observation Diary*. The personality reflects Arale’s innocence and curiosity, participating in her escapades while demonstrating fierce loyalty to the Norimakis.