Naming of moons underworld, and Nix (a respelling of Nyx), mother of Charon, is the goddess of darkness and the night. Kerberos is a giant three-headed dog who guards the entrance to the underworld. The fifth moon is named for the river Styx that forms the boundary between the worlds of the living and the dead. The name of Eris's moon Dysnomia was suggested by its discoverer Michael E. Brown, who also suggested the name of the dwarf planet. The name has two meanings: in mythology Dysnomia (lawlessness) is the daughter of Eris (chaos). However, the name is also an intentional reference to
Ghidorah, the Three-Headed Monster Yoshio Tsuchiya was originally attached to play Malmess but scheduling conflicts prevented him from participating. After the success of previous films where monsters were partnered up such as "King Kong vs. Godzilla" and "Mothra vs. Godzilla", producer Tomoyuki Tanaka decided to develop a film which would feature Godzilla, Rodan and Mothra. The film also includes a new monster, King Ghidorah. Ghidorah's design owes much to Japanese mythology. In 1959, producer Tanaka developed a film that retold the legendary stories of Japan. These included the tale of "Yamata no Orochi", an eight-headed dragon. King Ghidorah is based on Tsuburaya's design for