Genetically engineered alongside Experiment 101 (Roko) as Experiment 012, Lady Doubt is a purple cat with potent abilities: human speech, illusion-casting, and shapeshifting into human form. Her feline appearance features yellow eyes with light blue and black pupils, pink highlights above the eyes, a white club-shaped tail, and distinctive yellow and pink chest markings. Her human guise retains the pink eye highlights and presents in a purple and white jester outfit, purple gloves, and blue-tinted glasses.

She escaped her laboratory alongside Experiments 099 and Roko. Initially, she supported Experiment 099's antagonistic stance toward humans and his desire for retaliation. However, she established a moral boundary by opposing his plan to consume the captured young King (Spade) and Queen, advocating instead for dominating humans. When Experiment 099 disregarded her objections, she abandoned him. Subsequently, she allied herself with Professor Clover after he stole data from her former laboratory, becoming his dedicated assistant.

Serving Professor Clover with unwavering loyalty, Lady Doubt actively aids his criminal ventures as a violent thief. Her shapeshifting and illusion powers provide a key tactical advantage in his schemes. Significant past actions include chasing a young Joker (then Jack Jones) through ventilation shafts, instilling his lasting fear of cats, and collaborating with Shadow Joker (Cyan) during his tenure with Clover.