"Coatl" is a comet that was important to the Kaguya Island arc of the Sailor Moon musicals.
Nomenclature and Etymology
"Coatl" is the Nahuatl word for "serpent".
In the musicals, Coatl tried to crash into the Earth out of jealousy that was caused by the fact that the Solar System was brighter than Coatl. To prevent this disaster, Princess Serenity changed the orbit of Coatl. This would come as a cost, however, as it still ended up causing a major tidal wave that destroyed the kingdom of Artuka on Earth.