Juliette Douglas, more commonly known by her homunculus name Sloth, is a major antagonist in the 2003 anime adaptation of Fullmetal Alchemist. She is a homunculus, an artificial human born from a failed human transmutation. Her origin is directly tied to the protagonists, Edward and Alphonse Elric, who attempted to bring their deceased mother, Trisha Elric, back to life. The being that resulted from that forbidden ritual was a shapeless mass that was later given form and nurtured by the alchemist Dante, eventually growing to become Sloth, bearing the exact appearance of Trisha Elric.

Personality-wise, Sloth is a complex and tormented individual, a stark contrast to her namesake sin. Unlike the sluggish, muscle-bound giant from the manga and Brotherhood series, this Sloth is a sharp, cunning, and active character who serves as the Führer's secretary. Her primary internal conflict stems from the memories of Trisha Elric that are ingrained within her. She is haunted by visions of Edward, Alphonse, and their father, Van Hohenheim, memories that feel like her own but belong to the woman whose resurrection was attempted. This causes a profound identity crisis, as she knows she is not Trisha, yet she cannot escape the love and connection she feels for the Elric brothers because of these borrowed memories. This psychological torment is her defining trait, leading her to be cold, manipulative, and often mocking, especially towards Ed and Al, using her resemblance to their mother to unsettle them. She is generally apathetic towards others, rarely showing genuine emotion except for her eventual motherly affection towards the young homunculus, Wrath, and her deep-seated anguish over her own existence.

Her motivations are driven by a desperate need to resolve this identity crisis and alleviate her suffering. Sloth seeks to become a true human, a promise Dante uses to ensure her loyalty. She believes that by killing Edward and Alphonse, she can sever the lingering ties to her human template and prove to herself that she is not actually their mother, Trisha. In this way, her existence as a homunculus is a constant, painful reminder of what she is not, and destroying the brothers represents a chance to be free of that past and define her own separate identity.

Within the story, Sloth operates from a position of power and secrecy. Adopting the false identity of Juliette Douglas, she acts as the personal secretary to Führer King Bradley, who is himself the homunculus Pride. This role allows her to manage sensitive information and directly carry out the orders of Dante, the secret mastermind behind the homunculi, often coordinating missions with other homunculi like Envy. She is revealed to be a key asset in Dante's overarching plans, having been placed within the military's highest echelons through manipulated records following the Ishval Civil War.

Her most significant relationships are with her creators and her own "child". Towards Edward and Alphonse, Sloth feels a volatile mix of hatred and a twisted, lingering affection. She hates them for creating her and condemning her to a life of false memories, but Trisha's memories compel her to love them, a contradiction that fuels her rage. In contrast, she serves as a mother figure to Wrath, another homunculus created by the Elrics. While initially distant, she accepts his devotion, and he is one of the few beings she shows concern for, even as she ultimately views him as a tool to an extent. Her relationship with Dante is one of dependency and manipulation, as she believes only Dante can grant her humanity.

Sloth does not undergo a positive development arc but rather moves towards a tragic resolution of her inner turmoil. She remains a loyal agent of Dante until the end, driven by her desire to be rid of Trisha's memories. In her final confrontation with the Elric brothers, she is severely weakened by a lock of Trisha Elric's hair, a physical remnant of the human form she is based on. As she is defeated and her body is transmuted into ethanol, causing her to slowly evaporate, her final words are a calm and warm goodbye to Edward, telling him to "take care of each other". In her last moments, her hostility fades, and she seems to find a sense of peace and acceptance, finally embracing the maternal role she had fought so hard to deny.

As a homunculus, Sloth possesses a unique and formidable ability related to her namesake sin, but in a literal rather than behavioral sense: she can liquefy her entire body into water. This power grants her several advantages. She can use her limbs as high-pressure water jets for long-range attacks, slip through the smallest of cracks for infiltration and espionage, and drown her opponents by engulfing them. In her liquid state, she is incredibly difficult to harm with conventional physical attacks, and she can regenerate from damage by simply reforming as water droplets, making her effectively immortal unless specific counters are used. This ability also allows her to change her appearance and clothing, which helps maintain her disguise as Juliette Douglas. Her primary weakness is that she remains susceptible to alchemy that changes her chemical state, which is ultimately how Edward defeats her by transmuting her watery body into flammable ethanol.