The Fox Squirrel is an animal with a squirrel-like body and a fox-like head which first appears in Nausicaä of the Valley of the Wind and then in Laputa: Castle in the Sky and has cameos in other Studio Ghibli films.
The appereance is a mix of cats and kitsunes; like Evoli/Eevee in Pokémon. In Japan, both creatures are lucky charms for its owner. Fox Squirrels are called Kitsunerisu (キツネリス) oder Mammal (マメ) in Japanese.
Nausicaä of the Valley of the Wind
Laputa: Castle in the Sky
When Marnie Was There (Easter Egg)
In When Marnie Was There, a Fox Squirrel appears as a plush stuffed animal.