Luna and Artemis are the guardian cats of the Sailor Scouts. Their job was to revive and revive and regroup the inner senshi if the Dark Kingdom ever broke free. Luna revived every one of the inner senshi except for Sailor Venus, who was revived by Artemis. Artemis is Minako's guardian and Luna is Usagi's. Both Luna and Artemis had a hard time training their charges, because of their similarity in character. (Naoko has stated that both Minako and Usagi were based on her character). Later, during the Crystal Tokyo time they have a daughter named Diana. Diana becomes the guardian of Chibi-Usa aka Small Lady Serenity. In the Sailor Moon S movie Luna is turned into a human for a brief time. In the manga all of the cats have human form and are from the planet Mau. (note: only Luna is human in the anime. Artemis and Diana stay in "cat form" the entire time.)