Moony Loony is the moon of Moshi Monsters. She can be seen through the telescope which is located in the Obseratory. As Moshi Monsters itself does not have nighttime she is only shown sporadically. She appeared in Moshis vs Ghosts in House 3: "Full Moon Moshling".
She appears in the Moshi Monsters Food Factory (app), where an image of her is shown at the 'end of day' screen.