Pig, designated Computer Robot 78, serves among 100 Earth Defense Army robots as Number 1 at the Far East Base. His computational power rivals the base’s central computer, processing complex data, predicting anomalies, delivering weather forecasts, and consolidating eyewitness reports. Though initially mistaken for obsolete, he houses a robust emotional circuit enabling nuanced feelings and meaningful bonds, such as caring for orphaned Monkey.

Equipped with danger detection for abnormal radio waves and a language calculator for translating monster tongues, Pig functions as an intelligence officer and occasional combat pilot. He operates fighter jets during missions, providing analytical and combat support to the Science Guard Party. When newer Robot 101 arrives, Pig grapples with self-doubt over obsolescence. This escalates to an emotional crisis: repeatedly detecting Combugon’s signals—dismissed as malfunctions—he attempts self-decommissioning. His near-suicidal flight ends when Combugon emerges, confirming his warnings and restoring his confidence.

Later modified by Marume with a built-in gas stove, Pig gains cooking utility. During an excavation of Hectore, he disobeys orders to aid Ichiro Ogawara, becoming possessed by a liquid entity. The entity forces him to attack Marume until the gas stove expels the possessor, freeing Pig.

In the Heller Empire conflict on Planet U40, Pig shelters in Ultria’s ruins but disobeys orders to rescue teammates during Heller City’s assault. His resourcefulness proves vital in freeing the team after their capture by Mac Datar. Subsequent events include a rivalry with assistant robot Ulook 2001 aboard Ultria, and resolving a fusion mishap when mascot Monchi merges with an alien entity via an electron transmitter.

Standing 1.2 meters tall and weighing 90 kilograms, Pig features extendable legs for mobility and a torso compartment housing his grill. Post-Heller Empire defeat, he returns to Earth with the team, resuming duties without further documented incidents.