Oooh, maybe some smallish, humanoid-shaped fiend that appears to be composed of mucus and pus, who can lose its humanoid form and physically possess its master by slithering down their throat and into nose and ears?
Why do I think someone has a cold currentlY?
I keep thinking of those bouncing heads in Yubaba's office in Spirited Away. ^-^By the by, I'd love to know the folkloric precedent for these creatures in Spirited Away (if there is one). As with so many Miazaki films, it's hard to tell what's obscure folklore and what's just his awesome imagination.
There's an informative documentary for Spirited Away, it was in whatever version of the DVD release my daughter has. In it, Miyazaki revealed that some of the spirits in the film were actually satirical version he had made up himself, in response to figures in Japanese folklore. There are also actual pieces of folklore incorporated in the film, I remember some kind of game that he played as a child was one of them, meant to avert bad luck or something.
Yeah, the guy's amazing, and he certainly shops around for his folklore: Slavic, Celtic, Japanese...if you have or check out full versions of the disks, it'd be worth just watching all the extras to see what one could learn. (In my daughter's absence, I went to Blockbuster to take out Princess Mononoke yesterday, but was disappointed to discover it was just a bare-bones disk without all the nifty stuff she has.)
Those little coal dust guys in Spirited Away would make awesome familiars...