Toppo Jijo is a time traveler from the year 2,388,400 years in the future, accidentally crashing his spaceship on present-day Earth. This accident strands him permanently in the past. As a mouse from an advanced era, he uniquely communicates directly with humans, unlike other animals. His futuristic origin explains his distinct anthropomorphic design—blond hair, large ears, and a more human-like appearance compared to local mice.

Stranded in this new time, he forms a close bond with a human girl, Gina, who becomes his caretaker. His friendly and helpful nature helps him befriend local mice, including the fat Pierre and skinny Kurt, despite initial cultural differences. Toppo exhibits a mischievous and snarky side, particularly when provoking the antagonistic cat Megalo for amusement. This behavior reflects his inherent optimism and adaptability in facing the challenges of displacement. He learns that mice and cats are natural enemies in the present era—a stark contrast to their harmonious future relationship.

He evolves into a protector and unifier within his social circle, demonstrating consistent loyalty to Gina and his mouse friends. He often devises clever strategies to outwit Megalo and his feline minions. While distrustful of cats due to ongoing conflict, he extends kindness to non-threatening felines like Megalo’s mother and the kitten Tino. Traces of his technological background surface occasionally through inventions or futuristic knowledge, though his damaged spaceship remains inoperable, anchoring him to his new life.