Luna and Artemis are the talking cats that guide the Sailor Scouts and act as their earthly guardians. They inform the Scouts of their powers, and give them their transformation pens and their other devices.

When Luna first appears, she seems to be just Serena's pet cat. Luna gave Serena the magical locket that transforms her into Sailor Moon. She is also constantly nagging Sailor Moon to take her duties as leader of the Scouts more seriously. And Artemis first appears with Sailor Venus, as her guide and companion.