Oeufcoque Penteano began life as an ordinary mouse before experimental transformation reshaped him into a multidimensional polymorphic construct. This granted advanced intelligence and the capacity to shunt his mass between dimensions, enabling him to assume nearly any inanimate form—weapons, tools, or clothing—though he maintains he cannot become human. Designed as the world’s first and strongest hand-to-hand combat weapon, he functions as a unique Super Prototype All-Purpose Tool. Prohibitive costs and postwar political constraints prevented further production. His continued existence depends on proving his utility as a support entity for Mardock Scramble 09 case officers.

He most frequently appears as a small, gold-furred mouse. Enhanced sensory capabilities include an exceptionally keen sense of smell detecting subtle human emotional shifts. Omnidirectional receivers provide constant spatial awareness, making him highly effective for surveillance. Crucially, he possesses regenerative capacity, restoring his original form even after catastrophic damage or fragmentation, as when he regenerated following being blown apart.

Assigned by Dr. Easter, Oeufcoque partners with Rune Balot to aid her adaptation to cybernetic enhancements and assist in a legal investigation. Their dynamic evolves into profound mutual protection and emotional dependence. He routinely transforms into defensive items like bulletproof clothing or firearms to shield Balot, notably intercepting a lethal shot meant for her and suffering severe injury. His non-human origins limit his comprehension of complex human emotions, creating challenges in navigating Balot’s trauma and her burgeoning feelings; he often expresses confusion toward concepts like unconditional love.

His core identity remains anchored to his programmed purpose: serving as a tool to fulfill others’ needs. This constraint prevents deviation from his designated role. A defining past chapter involves his partnership with Dimsdale Boiled, which fractured when Boiled embraced murderous impulses, exploiting Oeufcoque’s abilities for violence and causing physical harm. This history resurfaces when Balot, consumed by vengeance during her pursuit of Shell Septinos, similarly misuses his powers. Witnessing her inflict grievous harm while experiencing pain akin to bleeding during forced weaponization triggers a critical rupture. Oeufcoque’s rejection of Balot compels her to confront her actions, mirroring his trauma with Boiled and underscoring the recurring cycle of abuse inherent to his existence as a sentient tool.

Throughout his journey, Oeufcoque wrestles with the ethical implications of his creation—an intelligent being bound by external constraints—while striving to uphold moral integrity amid surrounding violence and exploitation. His struggle accentuates themes of autonomy versus designed purpose within the narrative’s exploration of technological ethics.