It's more likely to be a reference to Goodnight Moon. The book has cats at the end saying 'Goodnight, Moon!'
Also there is no point in the series where Luna and Artemis actually stare at the moon together in this fashion, and the cat on the left is wearing a collar. Neither Luna nor Artemis is collared.
...
I was a six year old girl when Sailor Moon premiered in America. I know WAY too much about that show.
