While Jeannie is a sweet, kind-natured girl, her twin sister Jeannie II is the exact opposite. Dark haired and exotic, Jeannie II is a sneaky, devious genie who takes what she wants with no regard for the mortal world. Her actions, no matter how innocent they may seem, turn Tony's world upside down. her only desire is to steal Tony away from her naive blonde sister.

Barbara Eden's dual role as Jeannie's sister was so convincing audiences were left wondering if an identical actress had been cast. Eden claims that playing the dark-haired vixen was some of the most fun she had on the series.