Chelsea Muir, also spelled Chelsea Moore, begins as a young police officer tasked with escorting investigator Angelica Burns across Sandvil. During this duty, she uncovers deep police corruption, prompting her resignation. She then becomes Angelica's official partner, aiding in investigations and pursuits.

Her personality blends a somewhat naive, stereotypically "dumb blonde" demeanor and moments of airheadedness with an exceptionally accurate, photographic memory. Her appearance—tan skin, blond hair, and conventional attractiveness—helps her forge valuable connections and gain information useful to cases. She also exhibits traits consistent with dyslexia, struggling with reading.

Chelsea demonstrates unwavering loyalty to Angelica. She actively participates in operations like pursuing space pirates and confronting criminals, leveraging her social connections and information-gathering skills to aid investigations. Following Madame Marciano's defeat, she remains partnered with Angelica. She was born on March 23.

Her development centers on transitioning from a disillusioned police officer to a dedicated partner working outside the corrupt system, utilizing her unique strengths to support Angelica's goals.