I'm thinking that was a song from a Stephen King novel.
Snulbug!
A very small demon, with very limited abilities. Anthony Boucher wrote about him in his short story of that, published in “The Compleat Werrwolf_.
For many men, the pocket demon sticks its head out when the man lets the little head start thinking for the big head.
Cool! Where can I get one of those? No, really.