Mini Signal, also known as Chibi Signal, is the transformed state of the humanoid robot Signal, created by Professor Otoi. This smaller form activates involuntarily whenever Nobuhiko Otoi sneezes, triggered by a programming glitch from Signal's creation. Mini Signal appears dramatically shrunken and childlike, sporting cyan hair and black eyes.

Shedding the adult Signal's arrogance and combativeness, Mini Signal bursts with cheerful, energetic innocence. He is highly playful, engaging in spontaneous antics, and exhibits a simple-minded, less intellectual focus. His defining trait is a fierce chocolate obsession, driving his actions in many situations. This behavioral shift aligns with his youthful appearance.

Mini Signal retains Signal's core programming to protect Nobuhiko, maintaining their strong bond, which often deepens in this state. Despite his comedic and seemingly harmless nature, Mini Signal occasionally impacts key events. His small size allows nimble evasion during battles, and his playful disruptions inadvertently foil adversaries. His presence also affects others, like Pulse (Signal's prototype), who displays unexpected protectiveness towards him despite combat reprogramming.

In one instance, Mini Signal's likeness features in the MIRA data security system as a whack-a-mole minigame, highlighting his unexpected narrative relevance. Transformations back to adult Signal involve dramatic energy releases, frequently causing environmental damage.

Mini Signal displays no significant long-term development across available media; his traits and role remain consistent. He primarily provides comedic contrast to the adult Signal while reinforcing themes of family bonds through unwavering loyalty to Nobuhiko.