Quinzel was once a highly intelligent, calm, and compassionate young lady who worked at Arkham Asylum, before the Joker transformed her both mentally and physically into "Harley Quinn". After the Joker's manipulation, her mind and emotions were twisted to the point where she transformed into a person barely recognisable from the woman she once was. Harley is also quite tough and pathologically fearless. Quinn would become a homicidal, sadistic, child-like, and somewhat psychopathic villain.