Susan is a super genius scientist and the younger twin sister of Mary  as she is tomboyish and firm as her brother Johnny, but like her sister, Susan cherishes a deep love and obsession for Gil. Mary is a super-genius twin sister of Susan and the older sister of Johnny. Mary is more empathetic than her sister. Like her sister, Mary harbors affection for the next-door neighbor Gil Nexdor and they use their brother as a guinea pig for their dangerous experiment but they care about their brother 