Castor and Pollux are twin female youma under the control of Nephrite in episode 021 (Protect the Childrens' Dream! A Frienship Tied by Anime). Because they were Nephrite's strongest youma, their primary mission is to help him defeat the Sailor Senshi. The other part of their mission is to gather the energy of the young animator Hiromi Matsuno once she reaches her peak energy output. Nephrite puts his evil crest on one of Hiromi's animation pencils, causing her to become obsessed with drawing better images than her friend Kazuko Tadashita, and hastening her approach towards her peak energy output. Once Hiromi reaches her productive peak, Castor and Pollux immediately emerge from the pencil and drain all of the girl's energy. Kazuko, Usagi, Ami, and Rei are all on the scene. Kazuko faints,